Pantheon is a Greek word that means "all gods". The Pantheon is a Roman building in Rome, Italy that was commissioned under the reign of Augustus by Marcus Agrippa. The building was later rebuilt by the emperor Hadrian.
The dome of the Pantheon (seen in the two images above) is made of 4.5 tons of concrete that is supported by eight barrel vaults, and is concentrated on a ring of voussoirs. These structural elements allow the dome to be 142 ft. high at the oculus and the same length in diameter at the widest part.
The Pantheon's portico (pictured above) consists of 16 columns that were made in Egypt. The columns are each 1.5m in diameter, and were transported to Rome using barges and vessels. These 16 columns support a pediment that has an inscription attributing the Pantheon to Marcus Agrippa.
The Piazza della Rotonda (seen in the images above) is a rectangular square that has the Fontana del Pantheon and an Egyptian obelisk at its center. The square gets its name from Santa Maria Rotonda, the Pantheon's informal title. The fountain was constructed by Giacomo Della Porta under Pope Gregory XIII, and the obelisk was added under Pope Clement XI.
Click here for a video about the Pantheon.