Whenever Buddhism was introduced to a new region, Sumeru cosmology was transmitted to that region as well, since the basic framework of the Buddha’s teaching and its doctrine is based on it.

The Weltmodell centered on the cosmic mountain called Sumeru (or simply Meru, as su- is a prefix meaning “good”, “great”, “beautiful”) is a pan-Indian cosmic model that is not limited to Buddhism but also common in Brahmanism, Jainism, and Hinduism. Buddhist cosmology depicts the world as consisting of a vast plain with four large islands (dvīpa) lying in each of the four directions, with Mount Sumeru standing at the middle point of these four islands. Mt. Sumeru itself is surrounded by seven mountains consisting of gold as well as an additional iron mountain, with worldly oceans filling the space between each mountain. Jambūdvīpa, the island of the South, is supposed to be the place where humankind lives, while three other islands are inhabited by creatures of a mythological character.

Mt. Sumeru is an axis mundi connecting the earth and the heaven. On and above Mt. Sumeru are the multiple layers of the heaven.Footnote 1 Buddhist heaven is divided in three large realms in a vertical order, from the top down these are: the Kāmadhātu (the realm of desire), Rūpadhātu (the realm of form), and Ārūpyadhātu (the formless realm). Each is further divided into multiple heavenly levels, inhabited by heavenly residents of different classes; the higher the level, the higher the rank.Footnote 2 On the other hand, the underground world is reserved for the multiple layers of the hell; the lower the level, the worse the hell. The whole Sumeru world is repeatedly destroyed and recreated on a mahākalpa (great eon), a cosmic epoch of a tremendous period of time consisting of four kalpas (eons), lasting millions or billions of years.Footnote 3

Buddhism, which originated in North India around the fifth century BC, was transmitted to Central, East, South, and Southeast Asia. Frequently sponsored at the state level, Buddhist culture had a major impact on the formation of the philosophy and cultural landscape of wide areas of Asia by merging with the local culture. An inevitable process following its initial transmission involved considering solutions to conflicts between the Sumeru world system and the worldview already established in local cultural traditions. How then did the people in pre-modern Asian regions react to and incorporate Sumeru cosmology when accepting Buddhism?

This short essay provides a case study on the process of the transmission of India-originated Sumeru cosmology to East Asia along the so-called Silk Road by focusing on the Buddhist visual arts of two oasis towns, Kucha and Dunhuang, located in the border regions between the Indo-Iranian and Chinese cultural spheres around 500 AD (Fig. 1). This periodical focus is based on the presence of the earliest representations known that can be identified as Sumeru with certainty. In spite of their more or less contemporary date, the Buddhist paintings of these two regions bear the witness to completely different reactions to the visual symbol of Mt. Sumeru and its cosmological system.

Fig. 1
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Map of regional centers of the Eastern Silk Road. (© Alexey Akulov 2020)

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Sumeru Representations in Early Buddhist Paintings in Kucha

Kucha refers to a region that corresponds today with Kuche () in the Aksu Prefecture, Xinjiang Uyghur Autonomous Region in the People’s Republic of China. Blessed with abundant water and mineral resources, the historical city of Kucha was once one of the largest oasis towns to flourish on the northern edge of the Taklamakan Desert before the beginning of the Christian era. Moreover, situated along a branch of the Silk Road, which ran across the northern edge of the Tarim Basin and connected Central Asia with the western boundary of China, the Kucha Kingdom enjoyed great prosperity as a cultural crossroads connecting Eastern and Western Eurasia.

While the majority of the current population of the Kucha region today is Muslim Uyghurs, earlier inhabitants of this region were the so-called Tocharians, devout Buddhists who spoke Tocharian B also known as Kuchean, the easternmost branch of the Indo-European language group. Despite being over 2000 km from the Indian continent, Kucha belonged to the Sanskrit Buddhist tradition. The monks were acquainted with Sanskrit, the Indian language which was widely used as a “church language” in Central Asian Buddhist communities (cf. Nattier 1990), and thus were in direct contact with Buddhist teachings as transmitted through Sanskrit as well as the intellectual world of contemporaneous India it entailed.

A large number of the rock monasteries were carved around the area of the Kucha Kingdom during its Buddhist period, that is until around the tenth century. These rock monasteries, along with the inner décor of wall paintings, statuaries, wooden structures, and manuscripts discovered in and around them, are a rare repository of the local Buddhist culture. The peak of making cave monasteries in Kucha is considered to have been around the fifth to eighth centuries.

Wall paintings in caves with the so-called First Indo-Iranian style—generally thought to be the earliest type among different pictorial styles attested in this region dating to around 500 ADFootnote 4—contain some spectacular representations of the Sumeru world system. These present a “pure” Buddhist content, indicating how essential Buddhism was in the cultural and intellectual history of this region. The wall paintings of Kizil Cave 118 (Hippokampenhöhle) are the most prominent examples, in which the Sumeru world is visualized by full use of the three-dimensional space (Fig. 2a, b).Footnote 5 In all likelihood, all of the paintings of this transverse rectangular cave involve the story of King Māndhātar, a spectacular Buddhist tale about the rise and fall of a king with innate supernatural power between earth and heaven (Hiyama 2010, 2012).

Fig. 2
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a Left lunette of Kizil Cave 118 (Hippokampenhöhle, historical photograph taken by the Pelliot expedition in 1907. Paris, Musée Guimet, Photographic archive, 18-500534/AP7445. © MNAAG, Paris, Dist. RMN-Grand Palais/image musée Guimet/distributed by AMFGuimet Museum) b Drawing of the left lunette of Kizil Cave 118 by Monika Zin. (Zin 2020a)

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The cosmic order of the Sumeru world is mirrored in the spatial order of the murals. The representation of Mt. Sumeru in the shape of an hourglass is found in the lower half of the left lunette, which divides the heavenly realm above it and the earthly realm below. Namely, the scenes placed above Mt. Sumeru all illustrate scenes that occur in the Trāyastriṃśa heaven (“the heaven of the thirty-three deities”, located right on the peak of Mt. Sumeru), while the scenes below show episodes occurring in Māndhātar’s earthly palace. The mountainous landscape covering both haunches of the vault ceiling are part of the depiction of heaven; because some of the celestial realms are located on Mt. Sumeru, that is, above the sun and moon in orbit half way up the mountain (cf. Dietz 1994: 276), the mountain motif was associated with heaven in earlier Indian art traditions (cf. Zin 2015).Footnote 6 Above the heavenly mountainous landscape is a frieze running along the zenith, filled by celestial beings such as the mythological bird Garuḍa and a raincloud represented as the cloud containing entangled snakes. The heavenly realm is bordered by the frieze running through the cornices of both rear and front walls, occupied by mythical aquatic creatures that are extensions of the worldly ocean surrounding Mt. Sumeru.Footnote 7

Two multiheaded Nāgas (cobra deities) are coiled at Mt Sumeru’s narrowest midsection.Footnote 8 The presence of these two coiling Nāgas, along with the sun and moon revolving around the midsection of Mt. Sumeru, can be explained by references in several Buddhist cosmological texts.Footnote 9 Enigmatically, though, the reference to an hourglass-shape in early Buddhist texts seems unknown, even though this particular depiction of Mt. Sumeru had been widely accepted in early Buddhist art across Asia. The earliest clear references to this particular shape are, to the best of the present author’s knowledge, two commentaries in the Chinese translation of the Abhidharmakośa dated to the seventh century.Footnote 10 These texts can be regarded as evidence that the graphical symbol of the hourglass-shaped Mt. Sumeru had been firmly established in Chinese cultural sphere by then; the visual image might have influenced these textual accounts rather than vice versa. The formation process of the visual symbol of Mt. Sumeru needs further investigation.

Back to the discussion of the murals, two main protagonists, the superhuman king Māndhātar and the god Indra are represented facing each other in the corresponding positions, namely above the realm above Mt. Sumeru, on the opposite walls (Fig. 2a and 3). This is the representation of a narrative moment, when Māndhātar and Indra shared one heavenly throne; the supernatural power of the king was recognized as equal to that of the lord of heaven. After a while Māndhātar thought himself superior to Indra and thus wished to occupy the heavenly throne alone; through this evil wish, however, the king suddenly lost his supernatural power, falling off heaven to the earth below, and died uttering verses about the danger of greed (Fig. 3). This elaborate spatial arrangement turns the void space in the cave into a narrative stage in which visitors to this cave are not only involved in the thrilling narrative moment of Māndhātar and Indra making eye contact with their own intentions in mind, but can also navigate within the Buddhist geography. The three-dimensional space of this cave served viewers as a miniature model of the cosmos.

Fig. 3
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Right lunette of Kizil Cave 118 (Hippokampenhöhle, historical photograph taken by the German expedition in 1906. Asian Art Museum, State Museums of Berlin, B 1701)

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While focusing on another narrative subject, the murals of Kizil Cave 92 (Höhle mit der Äffin) repeat the same spatial arrangement to illustrate the landscape of Trāyastriṃśa heaven in the upper part of the cave. The front lunette shows the god Indra, the ruler of Trāyastriṃśa heaven, seated on the throne in his palace surrounded by his celestial retainers, while both haunches of the vault ceiling are filled by the mountainous landscape (Zin 56,57,; in press).Footnote 11 The rear lunette presents the Buddha meditating in a mountain cave, just having awakened from deep contemplation by the melody played by a heavenly harpist sent by Indra. The concept of decorating the upper part of the cave temple with the imagery of the Trāyastriṃśa heaven is consistent with Kizil Cave 118.

Another interesting representation is a pair of the Buddha’s sermon scenes, arranged at the middle of the facing side walls of Kizil Cave 207 (Malerhöhle), illustrating the cosmological/cosmogonic scenes at the end and the beginning of a kalpa (Grünwedel 1920: II. 24–25; Hiyama 2016: 122–138; 2017: 377–386; Figs. 4 and 5).

Fig. 4
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The Buddha’s sermon about the end of a kalpa on the right wall of Kizil Cave 207 (Historical photograph taken by the third German expedition in 1906, Asian Art Museum, State Museums of Berlin, B 812)

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Fig. 5
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The Buddha’s sermon about the beginning of a kalpa on the left wall of Kizil Cave 207 (Historical photograph taken by the third German expedition in 1906, Asian Art Museum, State Museums of Berlin, B 811, detail)

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The scene on the right wall (Fig. 4) visualizes the eschatological moment when the seventh sun rises and flame burns the world up to the uppermost level of the heaven, while the scene of the left wall (Fig. 5) visualizes the Buddhist genesis, namely the recreation of the world system at the beginning of a new kalpa, with primordial humans from the uppermost heaven reborn to fill the new-born earth. A Nāga king offering a bowl filled by treasure to the Buddha can be understood as an embodiment of the primordial water filling the primordial world. The ultimate subject of the latter scene, though, is the Buddhist refutation to the cosmogonic concept of Brahmanism. Brahmanism and Buddhism had been religious rivals in India during the Buddha’s lifetime and the following millennium. Brahmanic doctrine regards the god Brahmā as the eternal and omniscience creator-god, and those born in the social rank of Brahmins are considered descendants of the god Brahmā’, and hence bestowed with a superior position in society. The Buddha refuted this Brahmanic social-religious hierarchy, regarding Brahmā just as one of the ignorant sentiment beings without any influence on the repetitive process of destruction and recreation of the world, and rejected Brahmanic cosmology absolutely. In the painting, the Buddha is looking towards Brahmā and pointing at him with his right forefinger. Brahmā, who is depicted much smaller than the Buddha, hides himself behind Mt. Sumeru, as if he is ashamed and looks toward Buddha anxiously—this is a quite drastic visual propaganda against Brahmanism.

The presence of such radical scene is worth special attention, considering that Brahmanism had not been present in the region. Such a hostile attitude towards Brahmanic doctrine played no practical role in the region in a purely Buddhist climate of Kucha. This demonstrates what a direct, pure form of Indic Buddhism the Kuchean Buddhist people accepted—even including its attitude toward other religious streams in India that were not present in the region as part of the cosmological lore.

Sumeru Representation in Buddhist Paintings in Dunhuang in the Western Wei Period

Around 1400 km east of Kucha, Dunhuang () is another ancient oasis town in the current Gansu Province of China. Located at the northwest border of the Chinese cultural sphere under steady impact from the West, this multi-ethnic town, once an important hub of the Silk Road trade, became the cradle of a unique development in Buddhist culture.

Among various cultural influences brought from the west to this region, it was surely those from Kucha which left a clear trace on the formation of early Buddhist visual art in the Dunhuang area. Despite the long distance, these oasis towns were closely linked by the Silk Road trade network. Especially remarkable are the Buddhist caves from the Western Wei period, in the first half of the sixth century, which include various motifs common to the First Indo-Iranian style paintings in Kucha (for examples see Sudo 1989; Hiyama 2018). The situation of the acceptance of Sumeru cosmology in Dunhuang was, though, very different from Kucha. The westernmost town of the Chinese dynastic realm had strongly established Chinese cultural traditions, and it was the residents with Chinese cultural customs who became the main recipients of Buddhism imported from the West. In the process of accepting Buddhism, they had to confront a new worldview, namely the Sumeru cosmology, entailed in its doctrine.

In the Mogao Grottoes, the representative Buddhist site of the Dunhuang area where the Buddhist image-making activity continued over a millennium, the earliest Sumeru representation appears in Cave 249 carved in the Western Wei period, in all likelihood in the 530s.Footnote 12

Before taking a closer look at the wall paintings, it is important to consider the special geographical conditions of the region in this specific period. Dunhuang under Western Wei period was a time when cultural influence from both East and West drastically converged. The cultural wave from Central China had arrived through the appointment of “the Prince of Dongyang” Yuan Rong as a local governor of Dunhuang.Footnote 13 Yuan Rong was the fourth-generation grandson of Emperor Ming Yuan of the Northern Wei dynasty, and following his appointment in 525 he brought the latest cultural trends from Luoyang, the capital of Northern Wei dynasty, to this marginal area of the Chinese speaking world—most likely along with the immigrants and artisans from Luoyang who came with him. At the same time, Central Asia in the first half of the sixth century was at the beginning of a period often referred to as the Pax Hephtalica, namely the groups of people called the White Huns or the Hephthalites originally from Bactria who gained control of the vast territory starting from northern India, on the eastern periphery of the Sasanian Empire to the whole Central Asia region.Footnote 14 The geopolitical expansion of the Hephthalites contributed to accelerate traffic, logistics, and transfer of ideas owing to the smoothened trade network that linked the whole area of central Eurasia. Even though Dunhuang was outside Hephthalite territory, this geopolitical change clearly and directly influenced the Silk Road trade in which Dunhuang took large part. The presence of some Hephthalite and Sogdian donors portrayed in Mogao Cave 285 (cf. Ishimatsu 2010) reveals the direct contact and even immigration of people from Hephthalite territory to Dunhuang at that time.

The Sumeru representation on the western slope of the ceiling of Mogao Cave 249 was created with such historical background (Fig. 6a, b). Even at a glance, it is clear that the image is significantly different from the pure Indic Buddhist one from Kucha, with various new elements inserted in it. The shape of Mt. Sumeru itself, despite its dense representation that confuses one’s visual perception, is basically the same as seen in Kucha, an hourglass form consisting of blue-green, brown, and white mountain ranges, with two multi-headed Nāgas entangled at its midsection.

Fig. 6
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a Ceiling of Dunhuang Cave 249; b Mt. Sumeru depicted in Dunhuang Cave 249. (After Dunhuang Wenwu Yanjiusuo 1981: pl. 101)

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Interestingly, these Nāgas are clearly depicted as Chinese dragons with forelegs, while those in Kucha are depicted as multi-headed snakes, the traditional Indian Nāgas. A comparable representation is found in Yungang Cave 10 in Shanxi Province of China (Fig. 7), which was carved in the 480s and thus predates Mogao Cave 249 by about half a century.Footnote 15 The Yungang Grottoes were carved in the vicinity of Pincheng (or present Datong), the first capital of Northern Wei dynasty, by commission of the Northern Wei imperial house. The image-making of the Yungang Grottoes were supervised by the monk Tan Yao, who originated from Northern Liang, a dynasty based on Liangzhou (= present Gansu Province) that was conquered by Northern Wei in 439. Among the artisans engaged in carving the Yungang Grottoes are some forced to immigrate from Liangzhou to Pincheng as captives. The Buddhist art tradition of Liangzhou was deeply impacted by oasis towns in the Tarim Basin like Kucha (Su 1986). Although these two areas were distant from each other, they had close ties through the Silk Road network, and even belonged to same regional dynasties, the Former Qin dynasty and the Later Liang Dynasty, at the end of the fourth century. So it is no wonder that we find the same motif in Kucha and Yungang as the distance of over 3000 km was intermediated by the transfer of captured Liangzhou artisans to Pincheng. The transmission of the Sumeru motif back to the west occurred when the local governor Yuan Rong emigrated from Luoyang to Dunhuang along with the artisans. This observation demonstrates that a transregional transmission of an artistic motif over long distance is not a lineal process, but is intertwined with political changes, geographical shifts of power and the movement of artisans hired by powerful patrons.

Fig. 7
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Upper part of the entrance of Yungang Cave 10. (After Mizuno & Nagahiro 1952: pl. 23; © Institute for Research in Humanities, Kyoto University)

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Looking again at the mural in Mogao Cave 249, we see a demigod Asura standing in front of Mt. Sumeru raising the sun and the moon with his hands. This motif is associated with Buddhist cosmological lore concerning the Asura king, Vimalacitra, attempting to steal sun and moon, as narrated in several early cosmological texts (cf. He 1982; Duan 1983: 2–3; He 2006: 263–269; Tuzzeo in press). In contrast, a series of new elements appears around Mt. Sumeru, such as the thunder god encircled by drums and the wind god holding a cloth blown by wind, and a pair of figures sitting in Chinese-style architecture, and so forth. They apparently do not fit with the pure Buddhist Sumeru cosmology. These “Chinese” figures are further observed in the northern and southern slopes of the ceiling conflating the Sumeru imagery, including a pair of divine figures riding on mythical chariots flying toward Mt. Sumeru, along with various mythological creatures flying toward the western slope as well.

The identification of these apparently “Chinese” figures is still under dispute; some researchers explain them on the basis of a Taoist context, while the others are rather inclined to give a Buddhist interpretation to them.Footnote 16 One thing though is very sure; regardless of how many Buddhist connotations were given to such motifs, the visual language is borrowed from the Chinese visual art tradition, especially of the funeral context (cf. Tabayashi 2011: 240–1). The fact that this Chinese visual vocabulary could have been inserted around the Indic representation of Mt. Sumeru suggests that a very different cultural phenomenon occurred here from the case seen in Kucha.

It is most likely that the creation of such syncretistic image, as pointed out in some previous studies (He 1982: 32; Li 2013; He 2006: 263—294), is the product of the “Three-in-One thought”, which was a philosophical trend in Luoyang at that time. This refers to the philosophical movement to consider Confucianism, Taoism, and Buddhism as a harmonious aggregate, and thus to explain the doctrine of each teaching by rendering terms and notions of the others. In this movement, the Kunlun Mountain—the mythical mountain in ancient Chinese mythology which is said to be located to the west of China, where the queen of immortality resides along with other mythical creatures—overlapped with Mt. Sumeru.Footnote 17 The representation of a gate with a slightly opened door on the top of Mt. Sumeru is worth special attention in this regard. The motif of the slightly opened gate had been represented in Chinese art since Han dynasty, symbolizing the passageway to the heavenly realm placed above Mt. Kunlun (Saito 1995: 51–53). On the other hand, the gate is placed in the middle of the gray-colored (which is most likely the result of the discoloration of originally brighter pigment) buildings with zigzag walls, seemingly representing a city wall. The city located at the summit of Mt. Sumeru can be understood as the city of Sudarśana of the Trāyastriṃśa heaven, the inhabitants of which are often caught in conflict with the asuras.Footnote 18 This Sumeru representation masterfully projects both Kunlun and Buddhist cosmologies with their own coherencies, without conflicting with each other at all.

The Sumeru image of Mogao Cave 249 can be understood as a result of an attempt to present syncretistic worldview merging the Kunlun and Sumeru cosmologies. This could be a reflection of the domestic policy of the local governor Yuan Rong, who was not only a pious Buddhist by himself but also apparently employed Buddhism for solving conflicts and uniting powerful local clans. To govern the multi-ethnic, multi-religious milieu of the Dunhuang area, a syncretic worldview with a subtle balance between the Buddhism and Taoism in which neither of them are deemed as having a lower value than the other could have been utilized to unite the people beyond religious affiliations.Footnote 19

These observations of the Sumeru images in the wall paintings dated to around 500 in two major Buddhist sites of the Silk Road show that even when the basic form looks similar, the cosmological connotation entailed in each representation is quite different. In the case of early Kuchean paintings, the content is a direct import from Indian Buddhism, even including a rivalry with Brahmanic cosmology that was not at all present in the region. In the case of Mogao Cave 249, on the other hand, it was a syncretistic cosmography in which Buddhist and Taoist mythical figures coexist without any conflict with each other, the product of the ideological trend and political situation of the region. In addition, the presence of the Sumeru image in an intermediate form between Kucha and Dunhuang in the far eastern Yungang Cave 10Footnote 20 is most likely connected to the forced movement of artisans over long distances caused by the shift of regional political power. The Buddhist visual symbol of the “World” was slightly, but certainly, transformed as it crossed the cultural crossroads of the Silk Road by reflecting the localized expectation for Buddhism of each region.