Concentrations of megaliths, dolmens () and stone labyrinths dating between the end of the 4th millennium and the beginning of the 2nd millennium B.C. have been found (but little studied) throughout the Caucasus Mountains, including Abkhazia. Most of them are represented by rectangular structures made of stone slabs or cut in rocks with holes in their facade. These dolmens cover the Western Caucasus on both sides of the mountain ridge, in an area of approximately 12,000 square kilometres of Russia and Abkhazia. The Caucasian dolmens represent a unique type of prehistoric architecture, built with precisely dressed large stone blocks. The stones were, for example, shaped into 90-degree angles, to be used as corners or were curved to make a circle. While generally unknown in the rest of Europe, these structures are equal to the great megaliths of Europe in terms of age and quality of architecture, but are still of an unknown origin. In spite of the variety of Caucasian monuments, they show strong similarities with megaliths from different parts of Europe and Asia, like the Iberian Peninsula, Italy, France, Great Britain, Ireland, Netherlands, Germany, Denmark, Sweden, Iran and India. A range of hypotheses has been put forward to explain these similarities and the building of megaliths on the whole, but still it remains unclear. Approximately 3,000 of these megalithic monuments are known in the Western Caucasus, but more are constantly being found, while some are being destroyed. Today, many are in great disrepair and will be completely lost if they are not protected from vandals and general neglect. The North Caucasus Dolmens make up a lost city by the shore of the Black Sea. The dolmens could have been vaults of metal objects or jewelry that were pillaged by the invading Scythians around the first millennium BC. The dolmens could have been of spiritual significance, and are becoming cherished again today. Architecture of Circassian dolmens The dolmens have a limited variety in their architecture. The floor plans are square, trapezoidal, rectangular and round. All of the dolmens are punctuated with a portal in the centre of the facade. While round portholes are the most common, square ones are also found. In front of the facade is a court that usually splays out, creating an area where rituals possibly took place. The court is usually outlined by large stone walls, sometimes over a meter high, which enclose the court. It