Size and boundaries
The boundaries of Thingvellir national park are defined in paragraph one in the act on Thingvellir national park Act 2004 No. 47 1 June.
The boundaries of the national park at Thingvellir and the protected land shall be as follows: In the south, the boundary is a line drawn from the boundary of the farms of Arnarfell and Mjóanes on Langitangi, west across the lake to Grjótnes on the boundary of the farms of Skálabrekka and Kárastadir.
From that point, the boundary follows the boundaries of those farms to the boundary of Selkot and then the boundary of Selkot and Kárastaðir to the county borders of Árnessýsla and Kjósarsýsla on Há-Kjölur From that point the boundary follows the county borders to the source of the river Öxará at Lake Myrkavatn and to the peak of Hásúla, and thence in a straight line eastwards to the highest point of Mt. Gatfell.
From there, the boundary lies southward to Hrafnabjörg and along the eastern and southern boundary of the farm Gjábakki and along the eastern boundary of the farm Arnarfell in Langitangi.The protected area shall be under the protection of the Althing and remain the perpetual possession of the Icelandic nation.