We drive eastwards from Reykjavik, crossing the high moorland of Hellisheiði and passing south of the steaming volcano, Hengill. We also pass the greenhouses of Hveragerði village. East of Þjórsá river, we head inland and cross to the north of Mount Hekla, one of Iceland's most infamous volcanoes, which last erupted as recently as February 2000. We now enter the black Dómadalur (Valley of Doom), which is a gateway to Fjallabak Nature Reserve. The Nature Reserve is a huge mountainous wilderness that is constantly built up by ongoing volcanic activity and eroded by glaciers, rivers and wind. 

Reaching Landmannalaugar we have lunch, after which we start out by crossing the 500-year-old Laugahraun lava flow that is still giving heat to Landmannalaugar hot springs. Climbing steadily past numerous sulphur vents, we top a succession of rolling rhyolite hills before descending to the steaming hot springs of Stórihver. As we get higher, the better we can understand the forces of nature. Up on the plateau, steam rises in all directions from unseen vents and we reach our accommodation at Hrafntinnusker mountain hut in the late afternoon. 

Distance:12km (7.5miles) Active walking time: 4-5 hours Ascent: 470m 

 The idea that there is always some logic to landscape is proved to be false today, as we head south into the canyon complex to the south of Hrafntinnusker. Descending into the gorges of Jökultungur, we come across steaming hot springs and mud pools. The route winds southwards, crossing old snow patches and climbing ridges where we have views across dark volcanic plains towards lake Álftavatn and the Mýrdalsjökull and Eyjafjallajökull glaciers. Crossing the southern edge of the Torfajökull Massif, we descend a long slope towards the black sands and palagonite ridges around Lake Álftavatn (Swan Lake). Arriving at the lake, one of the most beautiful locations on our route, we check in at the Álftavatn mountain hut. 

Distance: 12km (7.5 miles) Active walking time: 4-5 hours Descent: 490 m (1610 ') GPS for the hut N 63°51.470 -W 19°13.640 

 Today there are several rivers to cross, as we head southwards and towards Myrdalsjokull Icecap. Some of these glacial streams and rivers are bridged, but others need to be forded. After a long, but gentle climb, we descend to the green oasis of Hvanngil, where there is a mountain hut. We continue our walk, crossing another couple of rivers, to reach the surreal 5- kilometer-wide, black sand plain of Mælifellssandur, beneath the conical peak of Stórasúla. Heading now towards Hattfell, another ancient volcano, we reach the Emstrur region where farmers used to graze their sheep in summer. Before arriving at the Botnar Mountain Hut (our accommodation for the night) we visit the magnificent Markarfljót canyon which is cut almost 200 meters down into the rocks south of Hattfell. Distance: 16km (10 miles) Active walking time: 6-7 hours Descent: 40 m (130 ') 

 The first challenge today is to cross the bridge across Emstrur River. Having overcome this obstacle, we trek through the magnificent Markarfljót Canyon, which was carved out by thundering floods, caused by volcanic eruptions under the ice cap. The effects of erosional forces are visible at every step on this trek and nowhere more obvious than in the Þórsmörk Valley. For the first time on our trek, we enter a green and well- vegetated valley, which becomes more luxuriant the closer we get to Þórsmörk. The last part of the hike is through thick birch forest, where even the lava ridges are covered with scrubby trees and the lovely arctic flowers that bloom for a few weeks each summer. Þórsmörk means Þór's forest and it is not hard to see why this area should be considered to belong to a norse god. It is out of this world! The valley is guarded on all sides by tremendous, fast-flowing rivers and steep glacier-clad mountains. It is one of the most beautiful spots in Iceland and the favorite weekend retreat of many of Reykjavik's hikers. We overnight at one of the Þórsmörk’s huts. 

Distance: 17km (10.5 miles) Active walking time: 6-7 hours. Descent: 300 m (985 ') 

 We spend the morning in Þórsmörk, with the option to take it easy and rest or to walk one of the numerous trails. One option is to visit Sönghellir Cave (Song Cave) or to hike up to the viewpoint of Valahnjúkur, from where we can see over the icecaps of Mýrdalsjökull (1460m) and Eyjafjallajökull (1666m). We catch the bus back to BSI bus Station in Reykjavik at 14.10. Arriving at approximately 18:45. We will walk to the guest house together and decide on a time to go out for dinner in Reykjavik.

Distance: 5-10 km (3-6 mi) Active walking time: 2-5 hrs

Group transfer to Keflavik airport for a return flight.  On the way we will stop at the Blue Lagoon to have a relaxing 2-hour bath its spa-like milky hot water. Considered one of the 25 wonders of the world, the geothermal water originates 6,000 feet below the surface, where freshwater and seawater combine at extreme temperatures. It is then harnessed via drilling holes at a nearby geothermal power plant, Svartsengi, to create electricity and hot water for nearby communities. On its way to the surface, the water picks up silica and minerals, before emerging at a soothing 38°C (100°F). Perfect for a relaxing and re-energizing bath. (B)