Marcus Agrippa's Pantheon is one of the world's most sublime architectural creations: a perfectly proportioned floating dome resting on an elegant drum of columns and pediments. It was built in 27 BC, and rebuilt by Emperor Hadrian in 120 AD. The temple has been consistently plundered and damaged over the years; it lost its beautiful gilded bronze roof tiles in Pope Gregory III's time. Look for the tombs of Raphael and Victor Emmanuel I.