Djuma Mosque is the oldest mosque in Derbent and one of the oldest in Russia. It was built over a 6th-century Christian basilica around 733-734 AD. It has a 15th-century madrassa.
There are three naves in the inside of the mosque. The width of central nave is 6.3 m, side naves are 4 m wide. The naves are separated by square columns 97 to 97 cm wide, that have profiled capitals. The columns are connected by lancet arches.
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.