The medieval Byzantine and Bulgarian fortress Petrich is located 4 km north of the town of Avren, Avren Municipality near the Black Sea city of Varna, in Northeast Bulgaria (not to be confused with the modern-day town of Petrich in Southwest Bulgaria); it is also 1 km away from the Razdelna railway station.
It is located on a high rock plateau towering at up to about 100 meters, on a territory of about 30 decares (app. 7.5 acres). It had an inner and outer fortress wall as well as stone stairs carved into the rock on the north side of the plateau.
Archaeological exploration indicates that the Petrich Kale Fortress was first established during the Early Byzantine period, in the 5th-6th century AD, but was destroyed towards the end of the 6th century AD.
(“Кale" is a Turkish word meaning “fortress" left over from the Ottoman period commonly used for the numerous ruins of ancient and medieval fortresses all over Bulgaria, whose proper names are sometimes unknown.)
It was rebuilt in the 11th-12th century, the period when Byzantium conquered the First Bulgarian Empire (632/680-1018 AD), and was a major fortress of the Second Bulgarian Empire (1185-1396 AD) during the 13th-14th century.
The Petrich Kale Fortress was completely destroyed in 1444 AD by the Ottoman Turks who had conquered all of Bulgaria in 1396 AD, after the Second Crusade against the Ottoman Empire led by Wladislaw III, King of Poland, Hungary, and Croatia, who perished in the Battle of Varna (which is why he is also known as Varnenchik – Warnenczyk in Polish).
The Petrich Kale Fortress was destroyed by the Ottoman Turks on November 7, 1444, three days before the Battle of Varna on November 10, 1444, in which the Christian Crusaders were defeated. Thus, the Petrich Kale Fortress is connected with the history of the Central European states Poland, Hungary, and the Czech Republic.
The Petrich Kale Fortress was first mentioned in written sources in 1154 AD by medieval Arab geographer Muhammad Al-Idrisi who described it as a “small thriving town" west of Varna.
Later it was mentioned by Byzantine poet Manuel Philes (ca. 1275-1345 AD) in connection with the military campaign of Byzantine general Michael Tarchaeneiotes in Northeast Bulgaria in 1278 AD.
It was also mentioned in documents of the Ecumenical Patriarchate in Constantinople in 1369 AD, and in numerous accounts of the Second Crusade of King Wladislaw III against the Ottoman Turks.
The Petrich Kale Fortress near Varna was excavated by Bulgarian archaebologists in the 1970s; in recent years, the archaeological excavations were resumed in 2010 by the Varna Museum of Archaeology (Varna Regional Museum of History).