Once the construction infrastructure was established in space, particularily in the the asteroid belt, it was relatively easy to construct huge space habitats, here we are inside Haven, the largest colony at the time, commisioned in 2221 and launched in 2230 AD.

Image Credit:
Image produced for NASA as part of a series of Space Settlement studies performed by NASA Ames Research Center in 1975-1976 which resulted in the NASA report "NASA SP-413: Space Settlements - A Design Study".