They called them insulae meaning "islands". They had no concept of fire escapes, and barely any plumbing (despite this image of Roman engineering). They really were the harris end of Roman architecture.

> the harris end

I guess that's the rear (or arse) end, if anyone else is puzzled and doesn't have a couple of spare minutes to chase it down ...

>> top floors were the least desirable. Poorer residents occupied the upper story.

Some writers placed Julius Caesar's aristocratic but down at the heel family in the lower floors of a Subura tenement, but apparently it really was a house.