Lutitsa Fortress, also known as the Marble City and Kaloyan's Citadel, is one of Bulgaria's best-preserved medieval fortresses located 5 kilometres southwest of Ivaylovgrad in the Eastern Rhodopes region. Originally constructed in the 4th to 6th centuries, the fortress gained prominence during the reign of Tsar Kaloyan (1197–1207) and served as a bishopric and later archbishopric centre for over 900 years. The impressive defensive structure features walls approximately 600 metres long and up to 10 metres high, with 8 of its original 12 towers still standing, including octagonal, round, and square variants. Archaeological excavations have recovered the citadel, donjon, two churches dating from the 10th and 15th–16th centuries, a necropolis with 15 graves, and remnants of ancient sewerage systems, providing invaluable insights into medieval Bulgarian life before the fortress declined and was abandoned in the late 18th century.
