Montes Apenninus

Not mountains in the terrestrial sense: the Apennines are the uplifted rim of the Imbrium basin, raised in minutes by the impact rather than over millions of years by tectonics. The range runs 600 km along the mare’s edge, with Mons Huygens reaching 5.4 km above the plain.

The inner face, toward Imbrium, is a steep scarp; the outer slope falls away gently into the highlands. Seen a day or two after first quarter, the peaks catch the sunrise while the plain below is still dark — the most dramatic sight the Moon offers a small telescope.