Castel Sant'Angelo (the Mausoleum of Hadrian), Rome

NOTES: Castel Sant'Angelo was originally constructed as a mausoleum for the Emperor Hadrian in 135-139 AD. The bridge, built at the same time to connect the mausoleum to the Campus Martius, was named Ponte Elio (Pons Aelius). When the mausoleum became a castle in 401 AD, it was renamed Castel Sant'Angelo and the bridge took the same name.