Until the mid-1800s, Seggiano’s great cistern collected all the rainwater for the village and offered a precious supply during the months of drought. Measuring 14 meters high, it is externally made of ‘Sasso Matrollino’, a very compact, sturdy, impermeable limestone rock which is also used in the foundations of houses in Seggiano. To ensure water-tightness, the inside of the tank is lined with shaped bricks in order to limit the use of mortar, with the radial sides converging in the centre of the tank and forming a perfect circle to reduce the critical points for the watertight seal.