Mare Insularum 7.0°N, 22.0°W

Mare Insularum (‘Sea of Islands’) isy a name first officially introduced by the IAU in 1976, and is therefore not found on older Moon maps. Mare Insularum covers an area of about 900 km in diameter. The centre lies roughly between the two crater Kepler and Encke (on the west) and Sinus Aestuum (on the east). The boundary in the north is formed by the Carpathians (Montes Carpatus). The southern boundary is indeterminate and here Mare Insularum merges into Mare Cognitum (another one of the IAU's recent names). The very young crater Copernicus (formed about 800 million years ago) and its bright ray system lie, like an island, in the ‘Sea of Islands’.

Hortensius 6.5°N, 28.0°W

Milichius 10.0°N, 30.2°W

Two circular craters lying west of Copernicus, with diameters of 14.5 km and 13 km, respectively. They are primarily of interesting in that they serve as landmarks for the visual observation or photography of one of the most interesting classes of lunar features, that of lunar domes. The observation of these structures (whose height normally amounts to just a few hundred metres) always requires illumination near the terminator, that is, a low angle of incidence of sunlight.

In this region of the Moon, individual domes and groups of domes may be readily observed. The are the largest lunar domes on the nearside of the Moon. In their form, gradient of their slopes and formation they may most readily be likened to terrestrial shield volcanoes. Directly west of Milichius is the dome Milichius Pi. North of Hortensium lies a group of six such domes.