Overview of the Tule Lake National Wildlife Refuge near Tulelake, California.  This birdless view shows Tule Lake as well as Gillems Bluff, a lava rim that runs north/south from the Oregon/California state line to Lava Beds National Monument.

Tule Lake is one of 20 listed lakes on Wikipedia classified as an ancient lake.  The lake is considered ancient if it is 1,000,000 years old or older.  It is ranked as #9 b/w 3-15 million years of age.