Þingvellir, anglicised as Thingvellir,[Note 1] 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 tectonic plate and the Eurasian. 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 (Icelandic: þjóðgarðurinn á Þingvöllum) was founded in 1930, marking the one-thousandth anniversary of the Althing. The park was later expanded to protect the diverse and beautiful natural phenomena in the surrounding area, and was designated as a World Heritage Site in 2004.

The name Þingvellir is derived from the Old Norse Þingvǫllr, from þing (“thing, assembly”) and vǫllr (“field”), meaning assembly fields. Compare the English thing and weald (“Thingweald”) from Anglo-Saxon þing and weald. The site takes its name from Alþing (Althing), the national parliament of Iceland, which was founded at Þingvellir in 930 and held its sessions there until 1798. A thing was a form of governing assembly found in Germanic societies, and a tradition that endures to this day in one form or another across Northern Europe.

Although the name Þingvellir is plural, the older form Þingvǫllr is singular, and the modern singular form Þingvöllur can still be heard.

The name is anglicised as Thingvellir, and might appear as Tingvellir, Thingvalla or Tingvalla in other languages. The spelling Pingvellir is incorrect: as the letter “p” should never be used to represent the letter “þ” (thorn), which is pronounced as "th" is in English.

Dingwall and Tingwall in Scotland, Thingwall in England, Tynwald on the Isle of Man, and Tingvoll in Norway bear names of the same root and meaning.

Source: https://en.wikipedia.org/wiki/%C3%9Eingvellir