In traditional Persian architecture, a howz (pool) is a centrally positioned symmetrical axis pool.

If in a sahn

Sahn

A sahn , in Islamic architecture, is a courtyard. As per the traditional Islamic architectural style, almost every mosque has a sahn, which is surrounded by an arcade from all sides. In Persian architecture, the sahn usually contains a howz, a symmetrical pool, where ablutions are performed...

 of a mosque, it is used for performing ablutions. If in a traditional house or private courtyard, it is used for bathing, aesthetics or both.

The howz is an essential element of the Persian garden.