Found 'dungeons'

Crap, the group is coming tonight and my maps aren't ready...  Well, I can pull any number of pre-genned dungeons or blank maps created by those creative souls out there, or I can rely on GIS to round up a real-world setting that can be modded and molded for use.

I need a small fort, perhaps a villa, or a gladiator school?  Well, here's ... a gladiator school.  Complete with floor plan and oblique views.

"Gladiator School found in Roman Austria..."

Crap, those goblin hoards are coming out of a cave system in the hills.  Here's one that will confound anyone's mapping...

Robber Baron Cave

Old mine, complete with side and plan views (ans a few buildings, to boot):

source

Another small mine complex

Odin Mine, U.K.

(I'll be discussing the geology and geometry of mines and caves in another entry)

Walled city?  We got plenty of 'em.  They may even by already labelled up with fortifications, temples, districts, markets, etc.

Dubrovnik

Lahore

Small frontier town with a blockhouse and ditch fortifications?

Early Albany, N.Y.

Here is the New York Public Library's digitized historical map library.  2000 pages of cartophilia.
http://maps.nypl.org/warper/maps

Repurposing existing place can be a handy shortcut for creating settings, especially ones where the place already comes with a number of the required features for world-building or plot generation.  Happy hunting...