The Basilica of Saint Clement, dedicated to Pope Clement I, is especially notable for its three historical layers. The 12th-century basilica is built on top of a well-preserved 4th-century church (with many frescoes), which was built next to a 3rd-century Mithraic Temple. For an admission fee, it is possible to explore the excavations of the lower two levels, which is a fascinating journey into the history of Rome.
This ancient church was transformed over the centuries from a private home that was the site of clandestine Christian worship in the 1st century to a grand public basilica by the 6th century, reflecting the emerging Catholic Church's growing legitimacy and power.
The current basilica was rebuilt by Cardinal Anastasius, ca 1099-ca. 1120. Today, it is one of the most richly adorned churches in Rome. The ceremonial entrance (a side entrance is ordinarily used today) is through an atrium surrounded by arcades, which now serves as a cloister, with conventual buildings surrounding it. Fronting the atrium is the chaste facade of Carlo Stefano Fontana, supported on antique columns, and his little campanile (illustration). The basilica church behind it is in three naves divided by arcades on ancient marble or granite columns, with Cosmatesque inlaid paving. The 12th-century schola cantorum incorporates marble elements from the original basilica. Behind it, in the presbytery is a ciborium raised on four gray-violet columns over the shrine of Clement in the crypt below. The episcopal seat stands in the apse, which is covered with mosaics on the theme of the Triumph of the Cross that are a high point of Roman 12th century mosaics.
The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.