Lake Masvatn has an area of 3,96 km². Its greatest depth is 17 m and it is situated 265 m above sea level on road no. 1 a short distance west of lake Myvatn.
A few brooks spill into it and its discharge is Maslaekur, which tributes the Reykjadalsa river. The catch consists of brown trout and lake char of equal size, 1-3 pounders.
The distance from the capital is about 460 km by the Whale Bay tunnel and 75 from Akureyri.