Ranikot is so big that it is often called the Great Wall of Sindh. Its walls climb and dip across the rugged Kirthar hills for around 30 kilometres, enclosing whole valleys, streams and smaller forts inside.
Nobody knows exactly who first built it. Historians have suggested Sassanian, Arab and local origins, but the walls we see today were largely rebuilt in 1812 by the Talpur Mirs, the rulers of Sindh, as a refuge and a guard on the western routes.
Inside are two smaller forts, Miri Kot and Shergarh. Ranikot has been on UNESCO's tentative list of World Heritage Sites since 1993, and it makes a popular day trip from Karachi and Hyderabad.
