Þingvallavatn is the largest natural lake in Iceland, located in Þingvellir National Park, which was the home of the world’s first democratic parliament (the Alþing), established by the Vikings in 930. Parliamentary sessions were held in this rift valley until 1799, after which parliament was moved to Reykjavik. This park was inscribed on the UNESCO List of World Heritage in 2004.

The rock mounds are cairns, which are often used as trail markers in many parts of the world. We saw large groups of them all over Iceland, so seems hard to believe they were marking trails and perhaps had a different use there.