Petavius est un exceptionnel cratère à fond fracturé de 177 Km et profond de 3300 m, à chaîne de montagnes centrale situé à l'extrémité sud de Mare Fecunditatis (Mer de la Fécondité). Le massif montagneux s'élève à 1 700 m d'altitude. Dans l’arène un système de rainures long de 80 Km orientées Nord-est Sud-ouest se révèlent lors d’une observation deux jours après la pleine lune (Jour 16 de la lunaison*). A noter une rainure radiale remarquable orientée sud-ouest qui relie la montagne centrale au bord du cratère Ainsi que quelques taches sombres. Le  rempart de son enceinte, qui se dédouble à l'ouest, s'élève par endroit à 3 300 m d'altitude et comporte de larges terrasses. Au Nord-ouest de Petavius se trouve accolé le cratère Wrottesley (57 Km) à piton central.

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Petavius is a large lunar impact crater located to the southeast of the Mare Fecunditatis, near the southeastern lunar limb. Attached to the northwest rim is the smaller Wrottesley crater. To the southeast are Palitzsch crater, Vallis Palizsch, and Hase crater. Further to the north is the large Vendelinus crater. The crater Petavius appears oblong when viewed from the Earth due to foreshortening.
The outer wall of Petavius crater is unusually wide in proportion to the diameter, and displays a double-rim along the south and west sides. The height of the rim varies by as much as 50% from the lowest point. The convex crater floor has been resurfaced by lava flow, and displays a rille system named the Rimae Petavius. The large central mountains are a prominent formation with multiple peaks, climbing 1.7 kilometers above the floor. A deep fracture runs from the peaks toward the southwest rim of the crater.
Rev. T. W. Webb described Petavius as "one of the finest spots in the Moon: its grand double rampart, on east side nearly 11,000 ft. High, its terraces, and convex interior with central hill and cleft, compose a magnificent landscape in the lunar morning or evening, entirely vanishing beneath a Sun risen but halfway to the meridian."
70cm radar images of this crater and its surroundings show that the region of the surface beyond the wide outer rampart of Petavius has a dark halo, characteristic of a smooth surface free of boulders. It is thought that this may have been created by radial outbursts during the original impact that swept the area "clean".
Crater Petavius B to the north-northwest of Petavius has a small ray system that lies across the Mare Fecunditatis surface.