A pair of O'Neill cylinders at Earth-Moon Lagrange point 5, or L5 for short. The cylinders are paired to maximize stability. Single cylinders have a limit on their length of 1.3 times their diameter, otherwise they start to precess. Having two counter-rotating drums balances out the angular momentum, allowing them to be built much longer. Secondly, by adjusting the rotation rate of each cylinder, you can steer the whole structure to keep it pointed on a specific axis, allowing constant sun-tracking for the mirrors and solar panels.
The actual spinning pressure vessels which serve as the habitats proper are nested within the non-rotating shells seen here. The outer shell provides radiation shielding as well as storage for bulk materials. Also visible are the kilometers of truss structure on which things such as communications antennae, storage tanks, cargo containers, freefall habitats, docking cradles, and other various infrastructure are affixed. A set of vast radiator panels bleed off the waste heat from the life support systems and industrial activities necessary to maintain the complex ecosystems and habitable environments inside the cylinders.
Each cylinder is about 2 kilometers in diameter and over 4 kilometers long, among the smaller size of such habitats.