Los Angeles, Rome, Gaul, Britain, Sandringham, Yaounde, Kolkata,
Lahore, Salt Lake City, St. Louis, Ohio, Illinois, Dublin, Paris, Kansas, Wales, South Pacific, Australia, Madrid, and I have seen Pentonville but not from the inside I'm glad to say.
Actually that's 37 not counting Pentonville Prison.
So that's actually 32 - 34 depending on whether or not New York and NYC count separately and whether Mindanao is the South Pacific or not.
I may have missed a few, but then this is not all its cracked up to be, is it. (Ever awakened and not be quite sure for a few minutes, what country you're in?)