Only 4km from Reykjahlíð, Bjarnarflag is a thermal zone on the lower slopes of Dalfjall, a long, faulted ridge pushed up by subterranean pressures that runs northeast to Krafla itself. Bjarnarflag has a small geothermal power station (Iceland’s first, built in 1969), whose outflow has been harnessed to create the Jarðböðin Nature Baths, the local version of Reykjavík’s Blue Lagoon. It’s an exceptional setting – fractured orange hills rise behind and the poolside overlooks Mývatn itself – where you can loll to your heart’s content in milky-blue waters heated to 38–40˚C. Just remove any copper or silver jewellery before entering the water, since the high sulphur content of the water can cause discoloration. In addition to the pool, there’s a café, hot pot and a couple of steam saunas.