The 5th-century Byzantine Erzurum Castle lies six kilometers from modern Erzurum. It is one of the few examples of fortified castles with towering towers, lighthouses and watch rooms. It is famous for its clock tower built in the 12th century by a well-known ruler of the Saltuklu dynasty. It is also worth a visit inside the castle building, the four doors bearing many inscriptions and decorations dating back to the Middle Ages and which attest to its importance as a major fortress along the Silk Road.