Near the east end of Tioga Pass Road, which leads into Yosemite, lies lovely Mono Lake. This body of water is unique in its tufa towers, which dot the lake. Mono Lake is also a natural aviary for seagulls. The shot of Jon, who is almost 6' tall, gives you an idea of the size of the towers (many were over 30 feet tall!). The sign tells how they were formed.
Answer to yesterday's "What am I" can be found here.