The Pantheon was a pagan temple until 609. In May of that year, it was converted into a Catholic church by Pope Boniface IV. It is called the Church of St. Mary of the Martyrs (Chiesa Santa Maria dei Martiri). The name is often shortened to Santa Maria Rotonda. 1,100 years would pass before the current high altar and this semi-dome crowning it were ordered by Pope Clement XI. They were created by papal architect Alessandro Specchi in the early 18th century. The rest of the Pantheon’s first floor is encircled with marble, columns and niches containing statues of saints. You might also want to watch for the sarcophagus of Raphael, one of Italy’s great master painters during the High Renaissance period.