Þríhnúkagígur, inside the volcano

Thrihnukagigur is the only volcano on Earth where visitors can take a lift down into the magma chamber. That sounds like marketing and is a plain statement of fact. It is a dormant volcano in the Brennisteinsfjoll volcanic system near Reykjavik, and the name translates as Three Peaks Crater. The chamber covers about 3,270 square metres and drops 213 metres, and the volcano has not erupted in some 4,000 years. What makes it unique is what did not happen. When most volcanoes fall quiet the magma in the chamber solidifies and plugs it, or the roof collapses into the void. Here the magma that filled the chamber drained away and the space simply stayed open, leaving a cavity the size of a cathedral beneath the surface. It was found in 1974 by the cave explorer Arni B. Stefansson, and it took until 2012 for it to open to tourism. It has been used for things other than sightseeing. In August 2015 the Icelandic band Kaleo and fourteen support staff descended into the magma chamber and recorded a live rendition of their song Way Down We Go. In 2016 the Secret Solstice festival announced that Chino Moreno of Deftones would perform the first ever public concert inside the magma chamber of a volcano. Only one tour of the chamber is available to the general public, and the season is short. Reaching the crater means a hike across the lava field before the descent even begins. The Inside the Volcano tour, run by 3H Travel, is the only trip into the magma chamber available to the general public.