An architectural wonder in simplicity, this domed temple was built in 27 B.C. as a tribute to all gods and then rebuilt in the second century A.D. by Emperor Hadrian.
It is one of Rome's best-preserved monuments, despite the removal of its marble walls, and bronze ceiling during the Renaissance.
The round temple includes a series of columns topped by a dome, which boasts a 30-foot opening to let in the light.
Up to now I couldn't figure out what happens if it rains!?

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