Khar-Balgas or Karabalgasun (“black city”) was the ancient capital of the Uighur Khaganate in the 8th-9th centuries, also called Ordu-balyk (“capital city”).

It is located on the territory of Mongolia, on the left bank of the Orkhon River, 17 km northeast of the ruins of the capital of the Mongolian Empire – Karakorum and 15 km north of the Buddhist monastery Erdeni-Dzu.
The city was destroyed and burned by the Yenisei Kyrgyz who captured it in 840. The capital of the Uighurs had a clear layout of multi-storey buildings. It was a large city surrounded by ramparts, behind which were suburbs, irrigation canals, arable land and gardens, the population of which reached 100,000 people. To the south-west of the central part of the capital, a fortress and a citadel were built, the walls of raw clay of which are still preserved to a height of 12 m, and the watchtower is 14 m. There was a palace inside the fortress, to the south of the fortress there was a temple complex and buildings- the farms of the Uyghur Khagans, as evidenced by the stele found here in the form of a dragon with inscriptions in Sogdian, Uighur and Chinese and dedicated to one of the Uighur Khagans who lived in the 9th century. The city and the fortress bear obvious traces of fire and destruction.

Khar-Balgas was discovered in 1871 by the Russian traveler Paderin, then described in 1889 by N. M. Yadrintsev and in 1891 by V. V. Radlov. Excavations were carried out in 1949 by a joint Soviet-Mongolian archaeological expedition led by S. V. Kiselev