Santi Quattro Coronati
The name of this ancient church is the Four Holy Crowned Ones, the martyrs. The saints, unamed, were soldiers who refused to sacricie to Aesculaptius and killed under order of Emperor Diocletian.
The church was built in the 4th Century. It was the center of activity at one time, but with after the Popes left for France (Avignon), even when they returned, they did not return to the Laternan, which is nearby, but rather the Vatican Palace, the the Bascilica Santi Quattro Coronti lost its importance.
Pope Pius IV entrusted the basilica and the surrounding buildings to the Augustinians, who still serve. In fact, to visit the cloisters, you must ring a bell and one of the nuns will open the door and let you in to visit the stunning cloisters.
In the 13th Century a Cosmatesque cloiser was added. This is a style of geometric decorations of inlay stonework done in the Medieval times. Cosmati was the leading framily workshop of marble craftsmen in Rome at the time.