Raudholar

Raudholar formed when lava from the Leitahraun flow ran over wet ground: the water flashed to steam and blew through the molten rock, throwing up cones of red scoria. These are pseudocraters - they were never vents connected to a magma source, only steam explosions in the lava's path - and about eighty of them stood here. During and after the Second World War the site was quarried heavily for red gravel to build roads and the Reykjavik airfield, and roughly half the cluster was removed before it was protected in the 1970s. What remains is a landscape of red bowls and pits, part natural and part excavation, with birch and lupin colonising it and paths between the cones.

The landscape

• Red pseudocraters - steam explosions in lava, not volcanic vents.
• Half the cluster gone - quarried for road and airfield gravel.
• Bowls and quarry pits together - natural and excavated forms mixed.
• Birch and lupin returning - vegetation colonising the scoria.

When to go

May to October. Two hours.

Things to know

Much of what looks like crater form is quarry scar, which is the honest reading of the site. There are no facilities. It is close to the city and used by runners and riders. Tracks are loose scoria and dusty in dry weather.

Nearby

Heidmork reserve adjoins it; Reykjavik is fifteen minutes north-west.