The Pantheon. The word comes from the Greek Pantheion, meaning "shrine to all gods." It was built as a temple to the seven dieties of the seven planets in the ancient Roman religion. Its exact age is unknown but most scholars credit its construction to the emperor Hadrian in approximately 126 A.D. It is the best preserved of all Roman buildings and has been in continuous use throughout its history. It is the oldest notable building on earth with its original roof intact. The inscription gives credit to Marcus Agrippa, who built the first pantheon in 27 B.C. That structure burned in the great fire of 80 A.D. to be replaced by the structure you see here. This building has served as the model for a number of famous buildings — Monticello, the home of Thomas Jefferson — being one of them. The Pantheon was consecrated as a Catholic church in 609 A.D. by Pope Boniface IV and dedicated to St. Mary and all Christian martyrs, signified by its new official name, Santa Maria ad Martyres. To every Roman however, and in every guidebook, it is simply the Pantheon.