Plana 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 on the boundary between two small 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...

 areas, with Lacus Mortis

Lacus Mortis

Lacus Mortis, latin for "Lake of Death", is a plain of basaltic lava flows in the northeastern part of the Moon. It lies just to the south of the elongated Mare Frigoris, being separated by a slender arm of rugged ground...

 to the north and the larger Lacus Somniorum

Lacus Somniorum

Lacus Somniorum is a plain located in the northeastern part of the Moon's near side. It is located at selenographic coordinates 38.0° N, 29.2° E, and has a diameter of 384 kilometers...

 on the southern side. It is joined to the crater Mason

Mason (crater)

Mason is the remains of a lunar crater that lies in the northeastern part of the Moon. It is nearly attached to the eastern rim of the flooded crater Plana, and southeast of Bürg. Along the northern rim of Mason is the southern edge of the Lacus Mortis, a small lunar mare...

 to the east by a short stretch of rugged ground. Due north of Plana in the midst of the Lacus Mortis is the prominent crater Bürg

Bürg (crater)

Bürg is a prominent lunar impact crater in the northeast part of the Moon. It lies within the lava-flooded, ruined crater formation designated Lacus Mortis. To the south and southeast is the crater pair Plana and Mason. To the west, beyond the rim of Lacus Mortis, is the prominent crater...

.

This is a crater with a slender outer rim that has been worn and eroded by impacts. This rim surrounds an interior that has been flooded by basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

ic 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...

, leaving a level surface with only a central peak at the mid-point projecting up through the floor. There is a small craterlet near the eastern rim, but otherwise the interior floor is nearly featureless. The outer rim has some narrow breaks along the northwest, and the side is lower along the southwestern face. A small, circular crater intrudes slightly into the northwestern part of the rim.

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 Plana.

Plana	Latitude	Longitude	Diameter
C	42.7° N	27.1° E	14 km
D	41.7° N	26.2° E	7 km
E	40.5° N	23.6° E	6 km
F	39.8° N	24.0° E	5 km
G	39.1° N	22.9° E	9 km