Geological Chronicle
Rhaeticus lies astride the equator of the Moon on the southeast edge of Sinus Medii. Dated to the Pre-Imbrian period between 4.55 and 3.85 billion years ago, the crater measures 43 kilometers wide along one axis and 49 kilometers long along another.
The rim traces the outline of a rough hexagon slightly elongated north to south, though its structure is heavily disintegrated. Its eastern wall remains the most intact section, whereas the northwestern perimeter has been reduced to a low rise and rifts breach the northeastern and south-southeastern walls. Lava later resurfaced the interior, leaving behind a floor interrupted by only a few low rises.
Beginning at the crest of the eastern wall, a chain of craterlets extends east-northeast for approximately one crater diameter. To the southwest, a long rille heads toward the crater Réaumur, masked near Rhaeticus by a group of mountains.