Lyell 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 lies along the eastern edge of the Mare Tranquillitatis

Mare Tranquillitatis

Mare Tranquillitatis is a lunar mare that sits within the Tranquillitatis basin on the Moon. The mare material within the basin consists of basalt formed in the intermediate to young age group of the Upper Imbrian epoch. The surrounding mountains are thought to be of the Lower Imbrian epoch, but...

, at the northern arm of the bay designated Sinus Concordiae

Sinus Concordiae

Sinus Concordiae is a bay on the Moon that lies along the eastern edge of the Mare Tranquillitatis. Along its northern border is an area called the Palus Somni, while the southern border is an area of irregular terrain that contains the ruined crater Da Vinci...

. To the north along the edge of 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...

 is the crater Franz

Franz (crater)

Franz is a small lunar crater that is located along the eastern edge of the Sinus Amoris, a bay that forms a northern extension to the Mare Tranquillitatis. It lies to the southwest of the prominent crater Macrobius...

. The region of terrain to the east of Lyell is named Palus Somni

Palus Somni

Palus Somni is an area on the Moon of relatively level but somewhat uneven terrain that lies along the northeastern edge of Mare Tranquillitatis and the Sinus Concordiae. It has selenographic coordinates 14.1° N, 45.0° E, and has a diameter of 143 km.The surface of this feature has low ridges and...

.

The outer rim of this crater is an irregular series of ridges in a roughly circular formation. There are multiple gaps through this rim, connected the interior to the mare in the west. The wall is at its thickest along the eastern side of the crater.

The interior floor has been resurfaced by lava, leaving a level, featureless surface that has no markings or impacts of note. The central region of the inner floor has a relatively low albedo

Albedo

Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

compared to the surrounding terrain, giving it a dark appearance that matches the nearby mare.

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 Lyell.

Lyell	Latitude	Longitude	Diameter
A	14.3° N	39.6° E	7 km
B	14.4° N	38.4° E	5 km
C	15.2° N	39.4° E	5 km
D	14.7° N	41.5° E	18 km
K	15.3° N	40.9° E	5 km