The Great Caucasus is a northwest-southeast-directed mountain range more than 1100 km long, located between the Black Sea and Caspian Sea. It represents an intracontinental tectonic system resulting from the Late Cenozoic structural inversion of a Palaeozoic-Mesozoic-Early Cenozoic back-arc basin (Dizi basin) in response to the convergence of the Africa-Arabian and Eurasian lithospheric plates. It is bounded to the south by the Transcaucasian massif, a palaeo-island-arc, and to the north by the Scythian platform. The Great Caucasus fold-and-thrust mountain belt is characterized by complete, intensive folding, mainly south vergent imbricated thrusting, close-joint cleavage etc. Structural relationships of the Great Caucasian fold-and-thrust mountain belt with the Transcaucasian massif and Scythian platform are, as a rule, tectonic overthrusts, but in some places the contacts are transitional. The Great Caucasus basin has developed, at least from Devonian, throughout Palaeozoic and Mesozoic to Early Cenozoic, as established by marine palaeontological data. Late Palaeozoic (Variscan) metamorphic and magmatic events, folding and topographic inversion are not observed in the Southern Slope Zone of the Great Caucasus. Variscan and Early Mesozoic (Old Cimmerian) orogenic events did not lead to closure of the Dizi back-arc basin. The mountainous Crimea (Triassic-Liassic Tauric series) represents a similar basin of continuous deposition with no Variscan and Old Cimmerian orogenic events and is generally considered to be the western extension of the Great Caucasian basin. East of the Caucasus, such a basin characterized by continuous Triassic-Jurassic marine sandy-argillaceous sedimentation is the Great Balkans (Transcaspian), which was continuously developing since the Palaeozoic. Throughout the whole Mesozoic, Palaeocene and Eocene, the Great Caucasus represented a domain accumulating thick terrigenous, carbonate, and volcanogenic marine deposits and only in Oligocene-Miocene it was transformed into a mountainous edifice between the Black Sea and Caspian Sea basins. At present, the Black Sea and Caspian Sea basins unconformably overlie different structures of adjacent land; their shoreline cuts several main tectonic units of the Caucasus and Crimea.