Þingvallavatn is the largest natural lake in Iceland, located within the Þingvellir National Park. It covers an area of about 84 square kilometers and reaches a maximum depth of 114 meters. The lake is known for its clear waters, which are fed by underground springs and glacial melt. The lake is situated in a rift valley, formed by the separation of the North American and Eurasian tectonic plates. This unique geological setting makes Þingvallavatn a popular destination for visitors interested in both nature and geology. The surrounding area is rich in history, as it was the site of the world's first parliament, the Althing, established in 930 AD.