St. Paul's Cathedral is the primary church of the Church of England, and the spiritual center of London. It withstood the Blitz back in WWI, most probably because the German bombers used it as a landmark.

In front of the cathedral stands a marble statue of Queen Anne, an 1886 replica of the 1712 original, which was badly scarred by the sulphurous atmosphere of 18th century London.

The cathedral itself is an impressive building, and we got a number of pictures:
Front view
Closeup of front
Side view

The crypt below the cathedral is also open to the public, so we got a few pictures down there, as well. While we didn't pay to go deeply in, it was worth a look around.
Some statues
Some more statues
Crypt Cafe entrance

That last one struck me as a little odd, but made a lot more sense when we went upstairs and read a bit about the place. It seems that St. Paul's is completely self-sufficient, receiving no money from the greater church.