Also known as Kaleto, the Belogradchik Fortress is an ancient fortress standing on the northern slopes of the Balkan Mountains in Bulgaria. One of the best-preserved fortresses in the country, it dates to Roman times and was expanded over the years by the Byzantines, Bulgarians and Turks. Covering 10,000 square meters and featuring walls over two meters thick and up to 12 meters tall, the fortress was last used for war during the Serbo-Bulgarian War in 1885. Set among spectacular rock formations that served as natural protection, the fortress almost blends in with its surroundings.
Today, the fortress is open to the public as an open-air museum. Visitors can wander through the three fortified courtyards, check out the defensive bunkers and climb up steep ladders to some of the highest rocks around the fortress.