National Museum survey in 1986-1988
In 1986 the Þingvellir Commission assigned the National Museum of Iceland to undertake the cataloguing of archaeological remains of human habitation at Þingvellir. In 1986-1992 an archaeological field survey was made at Þingvellir under the auspices of the National Museum of Iceland. Visible manmade structures in the assembly area were registered.
A precise system of coordinates was mapped in the area of the ruins and a map of the area made for use in planning work, including contours and the surveyed ruins . The area is delimited to the south by Hestagjá (Horse Gorge), to the north by Stekkjagjá (Sheep Fold Gorge), to the west by Almannagjá (Everymans's Gorge) and to the east by Nikulásargjá (Nikulás's Gorge). The ruins were mapped and plans drawn to a scale of 1:100.
This survey was not expected to reveal much that was new, as the area had previously been mapped and surveyed. In fact, however, this method of cataloguing yielded a far more accurate, and also far more disparate, picture of the area of the ruins than had been possible before. The ruins could be classified as belonging to older and more recent periods of construction. In some locations up to three or four layers of habitation are built one on top of the other. In addition to remains in Almannagjá and on Hallurinn and the plain beneath,Biskupabúðir, structures on Spöngin and Stekkjagjá were catalogued.
All remains visible on the surface were surveyed and plans drawn to a scale of 1:100, and the area was surveyed using a total station. These surveys were the basis of the planning map prepared for the Þingvellir Commission around 1990.