Castel Sant'Angelo- a weird multilayer cake
Wow, what a building. Originally the tomb of the Roman emperor Hadrian in ~100AD, the tomb was turned into a fortress in the 400s, and for hundreds of years kept the barbarians and goths out. Then in the 14th century the popes used it as apartments, including luxurious apartments with vaults for the treasure and soft porn art at the top. And to top it off, there is a covered ½ mile long elevated walkway from the vatican to here that several popes used to escape from the many enemies that threatened them. Do you think I made this stuff up?