This monumental church was designed by Michelangelo in 1561. It is 295 ft (90 m) long and 88 ft (27 m) wide, going 98 ft (30 m) in the air. It could have gone even higher, if Michalangelo had not leveled the floor with the street – the difference would have been 6.5 ft (2 m). Both the main and transverse nave were incorporated in the halls of Diocletian’s baths, caldarium and tepidarium. The two halls served Michelangelo to make a church in the shape of a Greek cross. Giant, red, granite pillars belong to the 1700-year old building. Appropriately enough, given that Pope Pius IV commissioned the building of this church, he was buried in it as well.
The meridian line
In 1700, Pope Clement XI established a commission to verify the Gregorian calendar.
This is why the meridian line appeared on the floor of the church, in order for astronomers and mathematicians to calculate the calendar.