Ranikot Fort in Sindh, Pakistan is the world's largest fort with a circumference of approximately 26 km or 16 miles. Since 1993, it has been on the tentative list of UNESCO World Heritage Sites.
It has an approximate diameter of 6 km. Its walls are on the average 6 meters high and are made of gypsum and lime cut sandstone and total circumference is about 20 km. While originally constructed for bow and arrow warfare it was later expanded to withstand firearms.
It is reputed to be the largest unexplored fort in the world. The purpose of its construction and the reason for the choice of its location are still unknown.
Ranikot is the most talismanic wonder of Pakistan and Sindh Province. Visible from five kilometers, its massive undulating walls twist and dip over the hills. With the circumference of about twenty kilometers, its walls, 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.