The Tehachapi Loop is part of the railway line between Bakersfield and Mojave in California.
On Sunday June 29 2003, we spent about an hour and a half at the Loop, watching and taking pictures of trains that went by. We saw four trains go around the loop, first two eastbound and then two westbound. When we were leaving, we saw two more trains waiting for eastbound access.
You can see a schematic map of the loop at Yahoo! Maps, a topographic map at TopoZone, an aerial view at MapQuest (also shown below), or a satellite view at TerraServer.