Stepwells (also known as vavs or baori) are wells or ponds with a long corridor of steps that descend to the water level. Stepwells played a significant role in defining subterranean architecture in western India from 7th to 19th century. Some stepwells are multi-storeyed and can be accessed by a Persian wheel which is pulled by a bull to bring water to the first or second floor. They are most common in western India and are also found in the other more arid regions of the Indian subcontinent, extending into Pakistan. The construction of stepwells is mainly utilitarian, though they may include embellishments of architectural significance, and be temple tanks. Stepwells are examples of the many types of storage and irrigation tanks that were developed in India, mainly to cope with seasonal fluctuations in water availability. A basic difference between stepwells on the one hand, and tanks and wells on the other, is that stepwells make it easier for people to reach the groundwater and to maintain and manage the well. 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. 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. A stepwell structure consists of two sections: a vertical shaft from which water is drawn and the surrounding inclined subterranean passageways and the chambers and steps which provide access to the well. The galleries and chambers surrounding these wells were often carved profusely with elaborate detail and became cool, quiet retreats during the hot summers. Names A number of distinct names, sometimes local, exist for stepwells. In Hindi-speaking regions, they include names based on baudi (including bawdi (), bawri, bawari, baori, baoli, bavadi and bavdi). In Gujarati and Marwari language, they are usually called vav, vavri or vaav (). Other names include kalyani or pushkarani (Kannada), baoli () and barav (). History The stepwell may have originated during periods of drought to ensure enough access to the water. The earliest archaeological evidence of stepwells is found at Dholavira where the site also has water tanks or reservoirs with flights of steps. Mohenjo Daro's great bath is also provided with steps on opposite directions. Ashokan inscriptions mention construction of step