Ancient city's remain Black Bull or Khadaasangiin ruins is located on the bank of Black Bull river, Khadaasan mountain on the eastside and 12 km far from the Dashchilen sum center, Bulgan aimag.

In XIX century, ruin was found and research was made in 1934, 1948-1949 and ruins were dug a little in 1970. This city's ruin is connected to two other historical times and first is Kidan dynasty from X to XI century. In order to build the fence of the city, soil was hardened lumpy and erected in rectangle type. It was four main doors which are (0.5x0.5 km size) located in 4 sides. The remains of the ditches around the city were found in four sides.

Two main streets which are aimed to west and east divide castles territory. There are dwelling house (some of them have special fences) were divided by 2 main streets which are aimed to west and east.  While making research on city's ruin, researcher found potteries and containers which is depended on IX century, are the same with the Uigur souvenir and also the vases and containers' decoration was popular among the people who lived on the bank the Black river and East Sea.

 The main basis which connects this ruin with the Kidan dynasty, is a pottery that was found from remain the Black Bull's ruin and also it is the same with vase on which Kidan scripts was written and found from Chin mountain's ruin. Later in the beginning of the XVII century Stone building were built in the city. This one consisted of several building which had firmly erected ramparts and the way lay stone and fortification were similar to the XVII century's fortifications. And those were built by Tibetan style. As local people say, "Nomgoi prince" Tsogt Taij established this place. Also his descendant polite Norovjantsan who lived in the beginning of the XX century thought alike.

The stupa of the Black Bull's ruin.

While 1970's research dig was made on one broken stupa and birch bark books which indicate remarkable Mongolian scripts culture and rare significant scientific work were found. These books consist of several types, pages are sized 7x4 to 14x5cm, all pages are bordered and decorated, and both sides of the pages were equaled by the numbers, made by the traditional way and many writers who were exerted highly. To classify those books by topics:
• Religious books
• Shamanism and Buddhism's customs, divination, forbidden writtens, spirits being tradition's books
• Legalism and law' books
• The alphabet of the Mongolian scripts
Among them the most important one is that brief copy of the law which drafted by the 18 rounds of Khalkh's four provinces, six provinces and seven provinces. In the brief copy of the law there are names of the historical people; Tusheet Han provinces Tuvmenhii Sain Noyon, Zasagt Han provinces Setsen taij, Darkhan Tusheet noyon, Daichin Baatar Noyon and Tsogt taij.

Remain of the Black Bull's ruin