The Buzovo Kale Fortress (“kale” is the Turkish word for “fortress” used in Bulgaria as a remnant of the period of the Ottoman yoke) is a Late Antiquity, Early Byzantine, and medieval Bulgarian fortress located in the Sarnena Sredna Gora Mountain near the towns of Buzovgrad and Kazanlak. In the Middle Ages it controlled the road between the fortresses of Kran and Boruy (today’s Stara Zagora) and the valley of the Tundzha River, defending the Kazalak Valley from attacks from the south. The so called Buzovgrad Megalith (a large stone used for a structure or a monument), which is dated to the Late Chalcolithic (Aeneolithic, Copper Age) and the Early Bronze Age, is located nearby. The Buzovgrad Megalith is also believed to have been a part of a larger Ancient Thracian ritual complex.
The Buzovo Kale Fortress has a rectangular form and an area of 17 decares (app. 4.2 acres). Its fortress walls were almost completely destroyed by the Ottoman Turks during their invasion of the Second Bulgarian Empire in the late 14th century. Parts of the fortress wall and a fortress tower have been preserved up to a height of 3-3.5 meters. It also had an underground tunnel to the Tundzha River which was used for supplying water. The artifacts found there include coins of Roman Emperor Constantine the Great (r. 306-337 AD), and ceramics from the Early Byzantine period and from the Second Bulgarian Empire (1185-1396 AD).
According to a Bulgarian legend, the Ottoman Turks invading Bulgaria at the end of the 14th century besieged the Buzovo Kale Fortress for 7 months before they managed to conquer it. The fortress was under the skillful command of Bulgarian voevoda (military leader) Buz who managed to fend off the Turkish attacks until the Ottomans brought the grand vizier Candarli Ali Pasha (in office 1387-1406 AD) from Albania. The vizier managed to capture a local child who revealed the entrance of the tunnel through which the defenders of the fortress procured water and food. Thus, after they were devoid of these vital supplies, Buz ordered the defenders and the local residents hiding in the fortress to leave at night and disperse into the woods of the Sredna Gora Mountain.