St. Clement Basilica, Rome

The church was built in honor of San Clemente, the fourth Roman bishop and pope. Beneath the church are the remains of a temple of Mithras, the remains of a Roman street, a warehouse and a patrician's palace. 
The most attractive in the church are the People's Barrier and the 12th century mosaic behind the altar, depicting the "Celebration of the Cross", and below it there is a marble gift box. 
Saint Cyril is buried in this church, who together with his brother Methodius created the Glagolitic alphabet. Later in Bulgaria it was developed by their students and in honor of Cyril was named Cyrillic.