A small town surrounded by Oakland in the Bay Area. Very prestigious to live in. Many people from Piedmont are characterized by being rich and snobby (which is sometimes true, but not all the time). Piedmont is located in the East Bay (the best part of the Bay Area), and in NorCal, AKA the better half of California.
Joe: Hey, dude, where do you live?
Sir Pinkington III: I happen to reside in the hills of Piedmont.
Joe: You mean... Piedmont? So what, you're rich or something?
Sir Pinkington III: Why, yes, yes I am. I inhabit a mansion on Sea View Avenue, the richest street in all of Piedmont.