Martvili Monastery sits upon the highest hill in the vicinity and was of strategic importance. The site upon the hill where the monastery stands today was used in ancient times as a pagan cultural center and was a sacred site. There once stood an ancient and enormous oak tree that was worshipped as an idol of fertility and prosperity. Infants were once sacrificed here as well. After the conversion of the native population to Christianity, the ancient tree was cut down so as not to worship it anymore. A church was originally constructed in the late 7th century upon the roots of the old oak tree and was named in honor of Saint Andrew who preached Christianity and converted the pagans across the Samegrelo region.
The main Martvili-Chkondidi Cathedral (Chkoni translates to 'oak') was reconstructed in the 10th century after invasions that destroyed the prior church. Preserved in the church are frescoes of the 14th to 17th centuries.
References: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.