The Slab Grave culture of the late Bronze and early Iron Age, related to the proto-Mongols, spread over northern, central and eastern Mongolia, Inner Mongolia, Northwest China (Xinjiang, Qilian Mountains etc.), Manchuria, Lesser Khingan, Buryatia, Irkutsk Oblast and Zabaykalsky Krai.
A vast Iron Age burial complex from the 5th-3rd century, later also used by the Xiongnu, has been unearthed near Ulaangom [REF].