Abhaneri Stepwell, Kalakho, India. This is one of the oldest "step wells" in India and considered to be among the biggest in the world. The incredible square structure is 13 stories deep and lined along the sides of three walls with double flights of steps. 3500 narrow steps arranged in perfect symmetry descend to the bottom of a well 20 meters deep to a murky green puddle of water. This step well provided the surrounding communities with a dependable source of water for centuries before modern water delivery systems were introduced.