Isidorus is a lunar

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 that is located to the north of the Mare Nectaris

Mare Nectaris

The Sea of Nectar is a small lunar mare or sea located between the Sea of Tranquillity and the Sea of Fecundity . Montes Pyrenaeus borders the mare to the west and the large crater near the south center of the mare is known as Rosse...

, on the eastern half of the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

's near side. It forms a pair with the slightly larger Capella

Capella (crater)

Capella is a lunar crater in diameter that lies to the north of the Mare Nectaris, in a rugged region with many small impact craters. It intrudes slightly into the eastern rim of the crater Isidorus, a feature only slightly smaller in diameter....

, which is attached to the east-northeastern rim. To the west-southwest across the lunar mare

Lunar mare

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...

 are Mädler

Mädler (lunar crater)

Mädler is a lunar impact crater located on the mare that joins Sinus Asperitatis in the north to Mare Nectaris to the southeast. To the west is the prominent crater Theophilus, and Mädler lies amidst the outer rampart....

 and the prominent Theophilus

Theophilus (crater)

Theophilus is a prominent lunar impact crater that lies between Sinus Asperitatis in the north and Mare Nectaris to the southeast. It partially intrudes into the comparably sized crater Cyrillus to the southwest. To the east is the smaller crater Mädler and further to the south-southeast is Beaumont...

.

The rim of Isidorus is circular and somewhat eroded, with several tiny craterlets lying across the northern rim. The interior floor has been resurfaced by lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

and is generally level, although it is marked by the small, bowl-shaped crater Isidorus A along the western rim. There is a tiny remnant of a craterlet attached to the northern rim of the latter formation.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Isidorus.

Isidorus	Latitude	Longitude	Diameter
A	8.0° S	33.2° E	10 km
B	4.5° S	33.0° E	30 km
C	4.8° S	31.7° E	9 km
D	4.2° S	34.1° E	15 km
E	5.3° S	32.6° E	15 km
F	8.7° S	34.2° E	20 km
G	6.4° S	31.6° E	7 km
H	3.9° S	32.6° E	7 km
K	8.9° S	33.3° E	7 km
U	7.9° S	31.5° E	6 km
V	8.9° S	30.8° E	4 km
W	9.4° S	32.3° E	4 km