Posidonius
What Posidonius is
Posidonius is a crater — a circular depression, almost always an impact scar — on The Moon, 95.1 km across, centred at 31.9° N, 30.0° E in the Mare Serenitatis quadrangle. It is the 399th largest named feature on The Moon and the 231st largest of its class there.
Where the name comes from
Of Apamea; Greek geographer (135(?)-51(?) B.C.). The International Astronomical Union approved the name in 1935, under the theme it applies to every crater on The Moon. Of the 1615 features of this class catalogued on The Moon, the naming categories run Germany (234), American (229), France (163), Great Britain (160).
What it would take to settle Posidonius
The Moon scores 29.1 as a world. That number is the same for every square metre of it — but sunlight, water, radiation and the ground under your feet are not. This is the same question asked at 31.9° N, 30.0° E.
What this spot has going for it is earth link — near side — Earth stands 47° above the horizon and never moves. What works against it is water — outside the ice-bearing latitudes.
Computed from Posidonius's catalogued latitude, longitude and feature class — 84% of the model's weight had a basis here, and one axis was dropped as not applicable to The Moon (radiation geometry). Gravity, pressure, delta-v and distance from the Sun are the same everywhere on The Moon and are already counted in the world's own index, not again here.
What this cannot see: elevation. Slope, local shadowing and the polar “peaks of eternal light” — ridge tops near the poles of a barely tilted world that catch sun almost continuously while a crater floor kilometres away never does — need a terrain model this does not have. Where a real mission targets a pole, that is usually why.
Posidonius's satellite craters
The IAU names smaller craters around a major one by letter. Posidonius has 13, and each shares the parent's namesake rather than carrying one of its own.
What is next to it
The largest crater features on The Moon
All 1,615 craters on The Moon — mapped together, with the naming theme and the size distribution.