GROUNDWATER

http://www.salve.it/uk
The massive project to save the city of Venice, Italy from land subsidence and rising sea levels

http://www.uh.edu/~jbutler/kunming/stoneforestkunming.html
A virtual field trip to the Stone Forest, Yunnan Province, China. - a region of typical karst formation.

http://www.3rivers.net/~dbaker/gndwater.htm
Water flows underground from mountains in Montana to Manitoba

http://www.geology.ewu.edu/ftrips/aquifer/aqtour.htm
Virtual Mystery Tour: Spokane Valley-Rathdrum Prairie Aquifer

http://www.beautifulrushmorecave.com/
The Black Hills Of South Dakota.

http://www.goodearthgraphics.com/virtcave/index.html
The Virtual Cave.  Explore various types of caves from your computer.