The Eurasian continent, when divided into main geoecological zones, resembles a three-layer "pie," in which various layers sequentially cover each other from north to south. The middle of the "pie" is the Great Steppe Belt of the continent. Stretching for eight thousand kilometers from the Black Sea to the Yellow Sea, this Belt served for many millennia as a domain of nomadic and semi-nomadic peoples. The relations of the nomads with their neighbors, and especially with the southern ones - settled agricultural cultures and civilizations - were almost always extremely complicated.