According to Wikipedia, a stepwell is a well “in which the water is reached by descending a set of steps to the water level.”
The builders dug deep trenches into the earth for dependable, year-round groundwater. They lined the walls of these trenches with blocks of stone, without mortar, and created stairs leading down to the water. The majority of surviving stepwells originally served a leisure purpose as well as providing water. This was because the base of the well provided relief from the daytime heat, and this was increased if the well was covered. Stepwells also served as a place for social gatherings and religious ceremonies. Usually, women were more associated with these wells because they were the ones who collected the water. Also, it was they who prayed and offered gifts to the goddess of the well for her blessings. This led to the building of some significant ornamental and architectural features, often associated with dwellings and in urban areas. It also ensured their survival as monuments.
The Chand Baori stepwell in India was built beginning in the 8th century CE and consists of 3,500 steps that descend 13 stories down.