Madame Monet has an interesting post on khattera, or underground tunnels, I think you'd be interested in. It has pictures, too, and some really neat historical facts. Go on over and learn about Morocco. I think you'll like her blog. Short excerpt:
Khattera are an ancient underground system of tunnels and wells, built several hundred years ago, to transport water long distances. It’s too bad they are being destroyed now. They can be found from Morocco to India, throughout dry regions of North Africa, the Middle East and into Central Asia. They were typically used in areas without any large rivers. Scholars think the technology originated in the Indus Valley civilization of Pakistan. They are known as khattara in Morocco, qanats in Iran, and suranga in India, with a few other names in between.