East of Húsafell, along Rte 518, the vast, barren lava flows of Hallmundarhraun make up a wonderful eerie landscape dotted with gigantic lava tubes. These long, tunnel-like caves are formed by flows of molten lava beneath a solid lava crust, and it's possible to visit several of them.

If you’ve got a 4WD, it’s also possible to continue into the interior along Rte F578 beyond Surtshellir, through the lakes at Arnarvatnsheiði, and on to Hvammstangi. Note that Rte F578 is usually only open seven weeks a year; see