The Ranikot Fort also known as Dewar-e-Sindh (Great Wall of Sindh), with a circumference of about 26 km or 16 miles, is reputed to be the largest unexplored fort in the world. Since 1993, it has been on the list of tentative UNESCO World Heritage Sites. It is located in the Kirthar Range, about 30 km southwest of Sann, in Jamshoro District, Sindh, Pakistan. Ranikot is the most talismanic wonder of Sindh. Visible from five kilometers away its massive undulating walls twist and dip over the hills. Its walls are built with dressed sandstone and reinforced with 45 bastions along the outer wall, of which 7 are rectangular and the remaining are round. All modified through the ages to accommodate the use of gunpowder, this perhaps makes it the largest fort in the world.
The original purpose and architects of Ranikot Fort are unknown. Some archaeologists attribute it to Arabs, or possibly built by a Persian noble under the Abbasids by Imran Bin Musa Barmaki who was the Governor of Sindh in 836. Others have suggested a much earlier period of construction attributing to at times the Sassanians Persians and at times to the Greeks. Although a prehistoric site of Amri is nearby, there is no trace of any old city inside the fort and the present structure has little evidence of prehistoric origins.
“The size of Ranikot defies all reasons. It stands in the middle of nowhere, defending nothing” writes Isobel Shaw. So why was this fort built here in the desolate terrain of the Kirthar range? Many theories have been developed to answer this question. According to Ishtiaq Ansari, the Talpurs had sent their families to Thar and Kachchh when Afsharids attacked Sindh during the times of Kalhoras. However, after acquiring the rule of Sindh, they wanted a safe and secure place where they could send their families during the troubled times. This might have prompted them to rebuild this fort to their needs.
Rahimdad Khan Molai Sheedai holds the view that its location in Kohistan on the western frontiers of Sindh gave it its strategic value. Whereas Mazher Ansari thinks that, it was first constructed in the Achaemenid Dynasty of the Persian Empire (550 – 330 BC). This empire stretched from Turkey in the west, where a similar wall was constructed near the Caspian Sea called The Great Wall of Gorgan, which is 155 km in length, and to the east up to River Indus in Sindh, where this majestic fort is located.