Lewis is a 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...

 on the far side 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...

. It lies along the western edge of the Montes Cordillera

Montes Cordillera

Montes Cordillera is a mountain range on the Moon. This feature forms the outer wall of peaks that surround the Mare Orientale impact basin, the inner ring being formed by the Montes Rook...

 mountains that surround the Mare Orientale

Mare Orientale

Mare Orientale is one of the most striking large scale lunar features, resembling a target ring bull's-eye. Located on the extreme western edge of the lunar nearside, this impact basin is difficult to see from an Earthbound perspective.Material from this basin was not sampled by the Apollo program...

impact basin. This crater has been heavily disrupted by the formation of the basin, and it is covered by ejecta from the impact leaving only an uneven depression in the surface. The outer rim is roughly circular, and the interior is uneven.