Here is a link to a place we visited last weekend in Rajasthan. Hundreds of years old, these step wells took five years for 2000 people to dig out to collect precious water. The one we saw was on the spice route to China and went so far down in the ground that it was truly frightening to take all those stairs down there.
http://www.archdaily.com/395363/india-s-forgotten-stepwells/