Borealis Planitia
What Borealis Planitia is
Borealis Planitia is a planitia — a low plain — on Mercury, 3,450 km across, centred at 67.3° N, 32.6° E in the Borealis quadrangle. It is the 1st largest named feature on Mercury and the 1st largest of its class there.
Where the name comes from
"Northern plain"; from classical albedo name for quadrangle. The International Astronomical Union approved the name in 1976, under the theme it applies to every planitia on Mercury. Of the 16 features of this class catalogued on Mercury, the naming categories run Latin (2), Greek (1), Ireland (1), Egypt (1).
What it would take to settle Borealis Planitia
Mercury scores 46 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 67.3° N, 32.6° E.
What this spot has going for it is ground — flat ground — the easiest thing to land on and build across. What works against it is water — outside the ice-bearing latitudes.
Computed from Borealis Planitia's catalogued latitude, longitude and feature class — 68% of the model's weight had a basis here, and 3 axes were dropped as not applicable to Mercury (radiation geometry, earth link, known ground). Gravity, pressure, delta-v and distance from the Sun are the same everywhere on Mercury 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.
What is next to it
The largest planitia features on Mercury
All 16 planitiae on Mercury — mapped together, with the naming theme and the size distribution.