A Taj Mahal of sorts, this temple was originally built by the Emperor Antoninus Pius to his deceased wife Faustina (who was deified after her death in 141 AD). The temple then became the temple to Antoninus Pius as well after his death (in 161 AD).
Like many other buildings from antiquity, the reason the outside frame of this structure survives so well is because the temple was converted into a church around the seventh or eighth century AD. The columns are made of cipollino (onion stone) marble and have Corinthian marble capitals.
Photograph shot from my trip to Italy in 2006.