The Salton Sea isn't really a sea at all, but instead, California's largest lake, formed over 100 years ago by a combination of heavy rains, snowmelt, and flooding of the Colorado River.
It's 226 feet below sea level and has 25% more salinity than the Pacific Ocean.
Ironically, it's become one of the largest stops on the Pacific Flyway and is home to over 400 species of birds.