The Þingvellir area is a part of the North Atlantic rift system, almost entirely nested within the Reykjaneshryggur-Langjökull rift system. It can be described as an area of sea-floor spreading, displaying the close association of crustal rifting and volcanism. Þingvellir and the Great Rift Valley of Eastern Africa are the only sites on Earth where the effects of two major plates drifting apart can be observed. Þingvellir is a national park in the municipality of Bláskógabyggð in southwestern Iceland, about 40 km northeast of Iceland's capital, Reykjavík. Þingvellir is a site of historical, cultural, and geological significance, and is one of the most popular tourist destinations in Iceland. The park lies in a rift valley that marks the crest of the Mid-Atlantic Ridge and the boundary between the North American and Eurasian tectonic plates. To its south lies Þingvallavatn, the largest natural lake in Iceland.
Þingvellir is associated with the Althing, the national parliament of Iceland, which was established at the site in 930 AD. Sessions were held at the location until 1798.
Þingvellir National Park (þjóðgarðurinn á Þingvöllum) was founded in 1930, marking the 1000th anniversary of the Althing. The park was later expanded to protect the diverse and natural phenomena in the surrounding area, and was designated as a World Heritage Site in 2004.
According to the Book of Settlements (Landnámabók), the settlement of Iceland began in AD 874 when the Norwegian chieftain Ingólfr Arnarson became the first permanent Norwegian settler on the island. Over the next centuries, people of Norse and Celtic origin settled in Iceland. Early on, district assemblies were formed, but as the population grew, there was a need for a general assembly. The descendants of Ingólfur who dominated the region of southwest Iceland had become the most powerful family in the country, and other chieftains felt a need for a general assembly to limit their power.