megastructure

[ meg-uh-struhk-cher ]
/ ˈmɛg əˌstrʌk tʃər /

noun

a very large, usually high-rise building or a complex of such buildings used for many purposes, as for apartments, offices, stores, theaters, and athletic facilities.
a very large, complex organization.

Origin of megastructure

First recorded in 1960–65; mega- + structure