The ancient Pantheon is one of the oldest and best well preserved monuments in Rome. It was built as a temple to the seven gods of the seven planets, in fact, Pantheon is a Greek word meaning "to honor all Gods."
It sits in the Piazza della Rotonda, a lively square filled with cafes, bars, and restaurants, the Pantheon we see today, although remarkably preserved, is quite different from the original rectangular shape that was built between 27 and 25 BC by Marcus Vipsanius Agrippa with only the inscription on the architrave which attributes the construction to Agrippa during his third office reading "M·AGRIPPA·L·F·COS·TERTIVM·FECIT" and the portico in front of the Pantheon, left to remind us of who its original creator was.

But instead, the majority of credit for this grandiose monument goes to Emperor Hadrian who rebuilt it between 118 and 125 AD.
It contains the largest masonry dome in the world but was surpassed by size when Brunelleschi finished his ingenious realization of the dome on the Florence Cathedral in 1434.
An interesting architectural aspect of the Pantheon is that the distance from the floor to the top of the dome is exactly equal to its diameter. The only natural light source to the Pantheon is from the oculus in the middle of the dome. The open oculus measures at 7.8 meters in diameter but the cleverly designed slanted floors and drains helps to remove what little rain might enter.
The Pantheon was consecrated as a Christian church in the 7th century, when the Byzantine Emperor Phocas donated it to Pope Boniface IV, which later saved it from plundering during years after during the medieval period.
From the time of the Renaissance period, the Pantheon has been used as a mausoleum and holds the tombs of the great painter and sculptor Raphael and Italian kings Vittorio Emanuele II and Umberto I and his wife Queen Margherita.