Named after the Mare Imbrium, Imbrium was the largest city on Luna. The structures on the surface were usually referred to as the "Old City" or "Old Town", while more recent underground dwellings were called the "New City". The oxygen used by residents of Imbrium came from excavation of ice below the surface.
Walking areas were mostly covered in magnetic metal, so that if one wore magnetic greaves they could simulate gravity.
A portion of the city of Imbrium was deemed the French Quarter, as it had a large French population. Moon walking was seen as impolite there.
When humans first settled Luna, they built massive steel domes on the surface to protect its inhabitants from micrometeorites and other hazards. The city built under these domes became known as the Old Town, as later most developments were constructed under the surface.