Belogradchik Fortress, Ancient fortress and museum in Belogradchik, Bulgaria.

Belogradchik Fortress, also called Kaleto, stands on the north slopes of the Balkan Mountains beside the town of Belogradchik. Its walls, over 2 m thick at the foundation and up to 12 m high, enclose three separate yards linked by gates across 10,210 m². Walls were built only from the northwest and southeast; elsewhere rocks up to 70 m high form the barrier.

Roman soldiers first built this fortress, and it was later expanded by Bulgarian Tsar Ivan Stratsimir in the 14th century. His additions strengthened the defensive capabilities with new fortified sections.

The name Kaleto comes from the Turkish word for fortress. The walls visitors walk today were largely rebuilt in the early 19th century under Ottoman rule, when French and Italian engineers added European elements to the Ottoman design. The site is managed by the Belogradchik Historical Museum and is part of Bulgaria's 100 National Tourist Sites, with a stamp available.

The fortress lies just outside Belogradchik on the northern slopes of the Balkan Mountains, and its three fortified yards connect through gates, so you pass from one to the next in sequence. Walls reach up to 12 m in height above foundations over 2 m thick, and the yards are enclosed by rock faces up to 70 m high. The site is managed by the Belogradchik historical museum and is part of the 100 National Tourist Sites; a stamp is available there.

The fortress integrates natural rock outcrops directly into its structure, particularly on the northwest and southeast sides. This created an unusual design where the landscape itself became part of the defensive walls.