An āb anbār آب انبار is a traditional reservoir or cistern of drinking water in Persian antiquity. The Persian phrase literally translates as "water reservoir".

To withstand the pressure the water exerts on the containers of the storage tank, the storage itself was built below ground level. One important aspect to consider here is their resistance to earthquakes. Many cities in Iran lie in a region that have been struck with massive earthquakes. However, since almost all ab anbars are subterranean structures capped barely above ground level, they inherently possess stable structures.

The construction material used for ab anbars were very tough and extensively used a special mortar called sarooj made of sand, clay, egg whites, lime, goat hair, and ash in specific proportions, depending on location and climate of the city. This mixture was thought to be completely water impenetrable. The walls of the storage were often 2 meters thick, and special bricks had to be used. These bricks were especially baked for ab anbars and were called Ajor Ab anbari. Some ab anbars were so big that they would be built underneath caravanserais such as the ab anbar of Haj Agha Ali in Kerman. Sometimes they would also be built under mosques, such as the ab anbar of Vazir near Isfahan.

The bottom of the storage tanks were often filled with heavy metals for various structural reasons. The 18th century monarch Agha Muhammad Khan, is said to have extracted the metals from the bottom of the Ganjali Khan public baths to make bullets for a battle

en.wikipedia.org/wiki/Ab_Anbar