Karst lakes form the dissolution of limestone and dolomite rocks. This lake, El Tejo, lies in a dissolved depression below the surrounding landscape (Cuenca Province, Spain). It is round, with a diameter of 130 m and a depth of 26 m. Researchers at the University of Valencia (Spain), and Utah State University (USA) have conducted numerous scientific analyses of the lake. The two small inflatable boats in the photo were back-packed down to the lake for sampling.