Rudimentary stepwells first appeared in India between the 2nd and 4th centuries A.D., born of necessity in a capricious climate zone bone-dry for much of the year followed by torrential monsoon rains for many weeks. It was essential to guarantee a year-round water-supply for drinking, bathing, irrigation and washing, particularly in the arid states of Gujarat (where they’re called vavs) and Rajasthan (where they’re baoli, baori, or bawdi) where the water table could be inconveniently buried ten-stories or more underground. Over the centuries, stepwell construction evolved so that by the 11th century they were astoundingly complex feats of engineering, architecture, and art.
http://www.archdaily.com/395363/india-s-forgotten-stepwells