Thingvellir National Park is the site of the original Parliament in Iceland - where the Vikings met for hundreds of years to discuss matters of law, commerce, and marriage. Thingvellir is also unique and interesting from a geological standpoint. The plains of Thingvellir are a popular destination for Icelanders and foreign tourists. Golden Triangle bus tours include visits to Thingvellir, Geysir, and the Gullfoss waterfall.

Iceland's Parliament was established at Thingvellir in 930 A.D., and is considered the oldest surviving parliament in the world. Each summer, families from all around Iceland would send a representative to Thingvellir, where the Lawspeaker would recite the laws of the land. Court cases were heard and decided, and new laws were discussed. In the year 1000 A.D., it was agreed that Iceland as a nation would convert to Christianity, althought the conversion was voluntary on the part of individuals and did not prohibit the older faith in Thor and Odin.

Thingvellir is a relatively flat plain surrounded by volcanoes on all sides. The Mid-Atlantic ridge runs through the area, which is tectonically active. There are many faults and chasms, and it is possible to measure here the movement of tectonic plates.

Thingvallavatn, or Thingvellir Lake, is the largest natural lake in Iceland. It is also the coldest lake on Earth that contains fish - the arctic char. The arctic char is a small fish related to trout and salmon, and its flesh is fluorescent orange.