From a site that seems to be of the authorities Google translates: "It was built by Badlis, one of the commanders of Alexander the Great, named after the city. (MÖ.312). It is on a steep rock block where two streams meet from the tributaries of Bitlis water. It is a fortified location extending from east to west. Its circumference is 2800 m. (4000 steps), the castle, 56 m. height and 7 m. It is recorded that there is a bazaar with a magnificent inn palace and 300 houses, 1 inn, 1 mosque and 1 minaret on the north side of the fortress, whose walls are not very strong, with three floors of iron doors facing down to the river, a bazaar and several hundred houses. . It was reinforced all around with 670 gratings. Under these open gratings, there are closed grating holes. Since the castle was built on a difficult and steep hill, there is no defensive moat around it. Watchtowers in the castle,It is stated in the sources that there are caves filled with supplies and ammunition. Today, only the castle is available and it has not lost its magnificent appearance with the repairs made from time to time. Apart from the castle, there was also a tower on the Dideban hill. This tower, which overlooks the mountainous neighborhoods of Bitlis , has only ruins. It is presumed to be a watchtower that marks the castle."

I here group pictures from its outside and some from the hill.