Þingvallavatn, also known as Thingvallavatn, is the largest natural lake in Iceland, located in a rift valley in the southwestern part of the country. With a surface area of 84 km2 and a maximum depth of 114 m, it's pretty impressive! The lake is famous for its historical significance as the site where the national parliament, Alþingi, was founded in 930 AD. Plus, it's surrounded by stunning volcanic landscapes and unique geological features, making it a popular spot for outdoor enthusiasts and nature lovers.