The Criminality map is reported as over 40,000 parts in a Roblox Developer Forum post about hiring map builders for the game. That’s the clearest figure I could verify from public sources.

Context

The same source says the map’s detail level hurts performance for low-end users, which fits why the part count is so high.

Quick note

Some Roblox games use much lower map counts, but Criminality appears to be unusually heavy and detailed by comparison.

TL;DR: about 40K+ parts.