[masklinn]

> Trantor in Foundation, just one huge mega-city that fabricates all of its needs

Trantor required continuous supply from 20 agricultural worlds to survive. Pretty much all necessities of life for trantorian were externally sourced, with the possible exception of water.

Once that shut down after the 260 sack and the Imperial Family leaving for Neotrantor, population crashed from 40G to 100M.