Fornaselsvatn is 10m above sea level and has an area of 0.19 km². It contains the same stock of the ice age brown trout known from Lake Þingvallavatn. The lake also has another brown trout stock that can be traced to Veiðivötn. The trout in the lake have reached a good size. It is about a 20- 30-minute walk to the lake. This should not put anglers off fishing there!