Arch construction in the mid-6th-century monumental defense system on the Rubas river in Western Caspian region

The study provided the latest archaeological materials of the mid-6th-century monumental defense system which was discovered in the Western Caspian Region on the Rubas River (Southern Dagestan) in 2014 and fully investigated in 2016-2017. The purpose of the study is to introduce new data on the fortification of the Eastern Caucasus obtained during the elaborate archaeological study of the monumental fortification on the Rubas River, namely the isolated multi-layered arch construction as its structural element. The material presented includes the reconstruction of the full range of its building, i.e. planigraphy, construction technology, architectural decisions, the circumstances of its destruction, and the features of the natural conservation. The purpose of its use is revealed, its monumental features and its typological correlation with the world-known fortifications of the early Middle Ages are identified. The massive stone block processing technology applied when building arched elements is determined. The Rubas fortification is compared with the world-renowned engineering strategic facilities of Sassanid Iran and Byzantium. The analysis of archaeological materials showed that the Rubas monumental fortification was not only a strategic long wall that prevented the invasion of migrant tribes in the Trans-Caucasian region and the Middle East but also a protection system for a large settlement.