Founded by Emperor Shah Jahan and surrounded by a magnificent 18m-high wall, this fort took 10 years to construct (1638–48) and is rumoured to have had the decapitated bodies of prisoners built into the foundations for luck. It once overlooked the Yamuna River, which has now shrunk to some distance away. A tree-lined waterway, known as nahr-i-bihisht (river of paradise), once ran out of the fort and along Chandni Chowk, fed by the Yamuna.