Desert dominates the central highlands, through which the Kjölur road winds its way
The Highlands of Iceland cover most of the interior of Iceland. They are situated above 400–500 metres and are mostly an uninhabitable volcanic desert, because the water precipitating as rain or snow infiltrates so quickly into the ground that it is unavailable for plant growth. This results largely in a surface of grey, black or brown earth, lava and volcanic ashes. A few oasis-like areas, such as Herðubreiðarlindir near Askja, are found only in proximity to rivers.
Icelanders categorise the Highlands as:
"Háls", meaning a broad mountain ridge between valleys, such as the one near Langavatn north of Borgarnes; or
"Heiði", meaning the real highlands, such as those alongside the Sprengisandur road.
The Highlands can only be crossed during the Icelandic summer (typically from June to August). For the rest of the year the highland roads are closed. The best known highland roads are Kaldidalur, Kjölur and Sprengisandur. Most highland roads require four wheel drive vehicles, because it is necessary to ford rivers. However, the Kjölur route can easily be traversed in an ordinary sedan and is therefore one of the more popular highland roads. Off-road driving ("road" in this context meaning tracks that are already present) is forbidden entirely in Iceland where there is no snow, including the Highlands, to protect the environment.