Petavius (110 miles) is a magnificent an exceptional formation. It is one of the lunar giants. The walls reach upwards of 2 miles above the floor and are heavily terraced. There is a central mountain mass that has several peaks and hills. The highest peak reaches up about a mile high. The floor is flat, but there are several rills. The largest and longest runs from the central peaks to the southwestern wall for over 30 miles and is mile wide. It is easily visible in my 2.4 inch refractor. In the 4 inch other rills become visible and the 6 inch reveals even more. Careful observation of the floor will reveal that parts are darker then others, especially in the north. If you are observing with at least 4 inches of aperture, look for a 3 mile crater on the floor to the southeast of the central mountains. If you are at a public observation 3 days after new Moon, be sure to show off this impressive formation.
Wrottesley (35 miles) is a fine crater abutting onto the western wall of Petavius. Its walls are terraced and there is a central mountain. While it is overshadowed by Petavius it deserves some of your observational time.