64.0518° N, 19.0313° W
Hnausapollur is blue crater lake located in the highlands, right before reaching Landmannalaugar. It is also known by another name, Bláhylur, that comes from the turquoise blue color of the lake. It was formed in 871, in a massive volcanic eruption that occurred in both Bárðabunga and Torfajökull glacier simultaneously forming a large caldera. A caldera is a large depression formed when a volcano erupts. The magma present in the magma chamber underneath the volcano is expelled, often forcefully and when the magma chamber empties, the support that the magma had provided inside the chamber disappears and the chamber collapses. Don’t be surprised if you see someone fishing down in the crater. The lake has some life, although fishing there is quite rare as the stream of water entering and flowing from the lake is all underground.
The lake is quite easily reached by 4×4 cars between the middle of June and end of September, when the highlands roads are open. Just follow road F208 on the way to Landmannalaugar and you’ll see a sign that says Hnausapollur.