You're right. Armageddon Echo is set largely in an elven ruin (and an associated pocket dimension).
Fair warning, though, the fall of that city is quite closely tied to Golarion's history. So, if you're running a homebrew setting, you may have to do some story tweaking.
They're not D&D/PF, but old MERP modules would have what you're looking for, and they will have detailed maps as well as rough conversion notes for AD&D.
A very quick scan through Ivid the Undying turned up two ruined Elven settlements in the Adri Forest, but only with a column or so of text each.