Thingvellir National Park, or Þingvellir, is a place in southwestern Iceland, near the peninsula of Reykjanes and the Hengill volcanic area. Þingvellir is a site of historical, cultural, and geological importance and is one of the most popular tourist destinations in Iceland. It is the site of a rift valley that marks the crest of the Mid-Atlantic Ridge. It is also home to Þingvallavatn, the largest natural lake in Iceland.
Parliament or Alþingi was established at Þingvellir in 930 and remained there until 1789. Þingvellir National Park was founded in 1930 to protect the remains of the parliament site and was later expanded to protect natural phenomena in the surrounding area. Þingvellir National Park was the first national park in Iceland and was decreed "a protected national shrine for all Icelanders, the perpetual property of the Icelandic nation under the preservation of parliament, never to be sold or mortgaged."
Information based on http://en.wikipedia.org/wiki/Thingvellir