Old St Paul's Cathedral
Building To 1666
From Engineering Timelines : "The present St Paul's Cathedral, designed by Sir Christopher Wren, is the fourth cathedral on this site. The first two Anglo-Saxon buildings were timber, and the third a Medieval stone structure with a timber roof. All three were destroyed in turn by fire — the third one was destroyed in the Great Fire of London."
Spitalfields Life has a good post: Relics Of Old St Paul’s At New St Paul’s.