Located north of Vatnajökull, Askja is a 50 sq km (31 sq mile) volcanically active crater or caldera, one of many craters in this area, which lies within the vicinity of the Dyngjufjöll Mountains in Iceland's remote central highlands. The region only receives around 450 mm of rainfall every year and is only accessible for a few months of the year. The Askja area was used to train astronauts for lunar missions, most notably as part of the Apollo training program.
Askja is a popular tourist destination and a great place for hiking, with the Askja Trail being one of the more famous routes. Alternatively, there are bus tours that take visitors in comfort through some of Iceland's largest untamed wilderness or on a lunar tour to take the inquistive in the footsteps of Armstrong or Aldrin where they prepared for their ultimate adventure. Bathers are catered for too in this diverse region. Close to the northeastern corner, for example, the lake Öskjuvatn has an active vent, which exploded in the eruption of 1875, leaving the crater Viti in its wake. Now, there is a warm lake in the crater that allows visitors to swim in water where temperatures average around 30 C. And, in the mountains surrounding Askja, visitors will find the impressive 'canyon on dragons' - the Drekagil, with a campsite and two mountain huts close by at Dreki. Those interested in the region's volcanic history will find two other volcanic systems of interest nearby, namely Kverkfjöll and Herðubreið.
The word askja is the Icelandic term for caldera and is used to describe similar volcanic formations at other locations. The mountains around Askja were formed from eruptions under an Ice Age glacier cap. For the most part, Askja itself emerged at the end of the ice age from a significant ash eruption that caused the collapse of the roof of the magma chamber at the heart of the central volcano. The rim of the deep circular depression that remained gradually filled with lava from subsequent eruptions, leaving Askja as it appears today.