Glory Hole, Lake Berryessa
Part of the Monticello Dam, this giant funnel drains overflow water from Lake Berryessa past the dam to the river below.
More info here.
Updated May 18, 2006: This is now an award-winning photo! See my blog for more information.
Updated October 28, 2006: See this image of me posing with prints I made. The photo accompanies my article "How to get big prints out of digital images", which appeared in the Oct. 28, 2006 Seattle Times.
[Appeared in Flickr's Explore page on Jan 16, 2006.]