An āb anbār is a traditional reservoir or cistern of drinking water in Persian antiquity.

Many traditional water reservoirs (ab anbars) are built with windcatchers that are capable of storing water at near freezing temperatures during summer months.

The pressure gradient windcatchers create sucks out rising hot air from inside the shaft while the colder dense air remains. The superb heat resistant material of the walls of the ab anbar further create an insulating effect that tends to lower the temperature inside an ab anbar, similar to a cave. 

The ventilating effect of the windcatchers prevent any stagnant air and hence any dew or humidity from forming inside, and the overall effect is pure, clean, cold water all year round.