Icelanders gathered at River Oxara in Thingvellir, The Parliamentary Plains, for the first time in 930 AD. From then until 1798, continuously for 868 years, Thingvellir was the nation's meeting place.

The first part of this period has been named "The Golden Age of Iceland". These words refer to the Icelandic Commonwealth that lasted from 930 to 1262. All this time, Iceland was an independent nation. The Althing (Icelandic Parliament) in Thingvellir held the supreme authority of the country. The Althing was both a legislative and judicial assembly. There, disputes from all over the country were resolved. In ancient times, the Althing convened each year at the end of June for a session of  approximately two weeks, but in later centuries, the session lasted  one week at the beginning of July.

During the "The Golden Age of Iceland", Thingvellir was the site of very many events related in the Icelandic Sagas. Most of these sagas were written in the 13th century and are the cornerstone of Icelandic civilization.

After 1262, Iceland became a part of the monarchy of the Norwegian King and later of the Danish King. The Althing nevertheless continued to convene in Thingvellir as a legislative assembly and judicial court up to the end of the 18th century. Signs can also be seen of general festivals being held during this period. Thus, Thingvellir, as in earlier times, was a centre of national life at the time of assembly each year.

In the 19^th century, several gatherings were held in Thingvellir. The most outstanding one was the National Celebration of 1874 when Iceland acquired its constitution. Poets then wrote poetry about Thingvellir, and the site became a symbol for all that Iceland is. In the 20^th century, Icelanders have held national celebrations in Thingvellir attended by a great many people. The most remarkable one was the Dedication of the Republic on 17 June 1944 when the Republic of Iceland was founded. From this occasion and others, Thingvellir has become, as the Act of 1928 on the Protection of Thingvellir states, "the sacred site of all Icelanders".

In addition to the above, Thingvellir is remarkable for reasons of natural science. The site of the ancient Althing lies in a rift valley. The basin is part of the Great Atlantic Rift that runs through Iceland from the South-west to the North-east. The rift valley basin in Thingvellir today has been formed over the last 10,000 years. Lake Thingvellir is the largest lake in Iceland and teems with life.

Thingvellir has been protected since 1928 and is the oldest national park in Iceland. The Thingvellir National Park is under the management of the Althing.