Lake Thrihyrningsvatn is situated at 585 m above sea level in the
central highlands quite far away from inhabited areas.
It has and area of 4,3 km²
and its greatest depth is 33 m. Its discharge, river Thrihyrningsa, later river
Arnardalsa, tributes to the glacial river Jokulsa á Fjollum. The lake is accessible
by car from different directions. It abounds in lake char, which used to be quite large
when the lake was netted regularly.
The distance from the capital is about 598 km by the Whale Bay tunnel.