The Pantheon, a word coming from a Greek adjective meaning "to every god," is the name of one of Rome's most famous buildings. It was built in 27 BC by Agrippa and rebuilt in 126 by Hadrian. It was intended to be a temple to all of the gods of Ancient Rome. It is circular and, even two thousand years after it was built, remains the world's largest unreinforced concrete dome. It is very well preserved, used as a Roman Catholic church called "Santa Maria Rotonda," and it is still open to this day.