Pantheon, Rome Built more than 1800 years ago, the magnificent Pantheon building still stands as a reminder of the great Roman empire. The building's dome, more than 43 meters high is most impressive. It was the largest dome in the world until 1436 when the Florence Cathedral was constructed. At the top of the dome is a large opening, the oculus, which was the only source of light. The front portico has three rows of 8 columns, each one with a diameter of 1.5m. A huge bronze door gives access to the cylindrical building. Its diameter equals the interior height of 43,3m. Church Originally a temple for all pagan gods, the temple was converted into a church in 609. The Pantheon contains the tombs of Raphael and of several Italian Kings. Its interior design contrast with the temple's structural design, but the marble floor still features the original Roman design. Earlier Temples Before the current Pantheon was built, two other buildings occupied the same site. The first one, a traditional rectilinear, T-shaped structure was buildt in 27 BC by the emperor Marcus Agrippa, son-in-law of the emperor Augustus. The temple was dedicated to the gods Mars and Venus. It burned in AD 80 but was rebuilt by emperor Domitian. In AD 110 the building was struck by lightning and burned again. In AD 118 emperor Hadrian commissioned for the Pantheon to be rebuilt but with a totally different design. This time the Pantheon building would last much longer. The Dome The most important problem the Romans faced during the construction of the Pantheon was the massive weight of the large dome. In order to support it without proper reinfor-cement, the thickness and type of concrete varies between the bottom and the top of the dome. At the base very thick (6m, 20ft) walls were constructed. At the top of the dome, a lighter type of concrete was used and near the oculus it is only 7.5 ft or 2.3 m thick. The use of coffers in the ceiling and the opening at the top also helped reduce the weight of the dome.turkeyarena.com The Columns The huge, 60 tons weighing columns used for the portico were quarried in Egypt. They were transported all the way to Rome using barges and vessels. The columns support a pediment with an inscription attributing the Pantheon to Marcus Agrippa even though it was built by Hadrian. Piazza della Rotonda The Pantheon borders the Piazza della Rotonda, a rectangular square with a central fountain. It is situated in the historic center of Rome, not far from the Piazza Navone.