Soon after the tours start we will cross Hólmsá at a place called Gudduós at Miðdalsheiði, thereafter we will gratually climb up to Mosfellsheiði.
Mosfellsheiði is heighest 410m above sea level. Big relative flat land between Esja to the north and Hengill to the east. Covered with moss and some lava in the south.
The Hellisheiði Power Station is the eighth largest geothermal power station in the world and largest in Iceland. The facility is located in Hengill, southwest Iceland, 11 km (7 mi) from the Nesjavellir Geothermal Power Station. The plant has a capacity of 303 MW of electricity and 200 MWth of hot water for Reykjavík's district heating. The power station is owned and operated by ON Power, a subsidiary of Reykjavík Energy.
The mountain is south of Lake Thingvallavatn , south-west of the Nesjavellir geothermal area, south of Þingvellir National Park and is the most prominent part of a volcanic region that extends to the coast. South of the mountain towards the coast is the Hellisheiði geothermal area to its south-west, and the town of Hveragerði on Iceland's main ringroad, Route 1 about 45 km (28 mi) east of Reykjavík. At the coast is the port of Þorlákshöfn. Hengill is 803m at its heighest.