Tonight, on the National Geographic channel, there was a show called
Secrets of Florence. It discussed the rulers, artists, and thinkers of renaissance Florence. Among other things, it showed the half-mile-long passage that Cosmo MeDici used to move through the city without having to mingle with the commoners and even his own servants.
When I saw it was on, I immediately thought of
GURPS Hot Spots: Renaissance Florence. If you're interested in the subject, you might want to catch that show.