Kokalyanski Urvich, Medieval fortress and archaeological site in Kokalyane, Bulgaria.

Kokalyanski Urvich is a ruined medieval fortress on the Sredobardie ridge of the Lozen mountain, on the right steep bank of the Iskar River about 20 km from central Sofia on the road to Samokov. One defensive wall survives well, together with part of a defence tower 7 m high and the foundations of the church of Sveti Iliya. The standing wall is built of irregular grey and brown stones in rough horizontal courses, thicker at the base and tapering to a broken top, with a second lower mass of similar stonework beside it.

Probably founded in the 9th–10th century, Urvich was known in the time of Tsar Samuel as Eskumane, after the river Eskus (today Iskar). It served as the main base of Tsar Ivan Shishman's troops and, according to historians such as Yordan Andreev, of his brother Ivan Asen V, called Tsar Yasen by locals, who died in a battle near the fortress in 1371. It fell with the capture of Sofia by the Ottomans.

Local songs and legends call the fortress's last defender Tsar Yasen, a name historians link to Ivan Asen V, son of Ivan Alexander. The village name Kokalyane is said to come from piles of bones left after a battle nearby in 1371. The fortress church of Saint Elijah later continued as a monastery.

The site remains accessible year-round via hiking trails that begin from the village of Kokalyane and lead to the fortress. Visitors should prepare for uneven ground and potentially slippery sections, particularly after rain or wet weather.

The fortress is also remembered for a defensive trick: the waters of the Iskar could be diverted by a movable dike, making the stronghold unreachable and allowing it to withstand long sieges. The river meander below the walls is a declared natural landmark.