St Paul's Cathedral, London By Sir Christopher Wren. The site faced that of the church destroyed in the Great Fire of London in 1666
St Paul's - Rome, Italy (Yes, the Vatican quarters are technically also a regal palace!
30 famous places that you MUST see - St Paul Cathedral in Harissa, Lebanon
Paul's Cathedral in London, England. I remember walking past this place and it looked quite magnificent despite the grey-ish London skies.