Synonyms for Built-up:

n.

citified, civic, cityscape, city planning, citywide, charter, civilization, city. built-up (noun)
settled.
developed (noun)
full, Overbuilt, congested, overdeveloped, growing.

Other synonyms:

citified, city planning, citywide, civic. overdeveloped, civilization. city. charter. Other relevant words:
city, civilization, charter, overdeveloped, citywide.