The tufas at Mono Lake, thirty minutes north of Mammoth, are a spectacular sight. The first time I visited the South Tufa area, I was sure that I was walking on the moon. When calcium-rich water comes into contact with carbonate-filled lake water, limestone tufa towers are created. The towers were exposed when the lake level dropped significantly.
During the summer, there are daily guided tours, or you can take a self-guided walk. The South Tufa area costs $3.00 for adults; children under 16 are free.