Anuradhapura has three great tanks. Nuwara Wewa, is the largest, covering about 12 sq km. It was built around 20 BC and is well away from most of the old city. The 160-hectare Tissa Wewa is the southern tank in the old city. The oldest tank, probably dating from around the 4th century BC, is the 120-hectare Basawakkulama to the north. Even today these tanks are being reserved and provide water for farmers in the area during the rain-free seasons.