Some of the most stunning architectural structures in India are to be found below ground: these are its stepwells, ancient water stores. Stepwells are unique to India and from around the 3rd century CE were built throughout the country, particularly in the arid western regions. Excavated several stories underground in order to reach the water table, these cavernous spaces not only provided water all year long but also fulfilled other functions; they offered pilgrims and other travelers a respite from the heat, and became places in which villagers could socialize. Stepwell construction evolved...