If you only visit one place in the Iceland highlands, make it Landmannalaugar. The name translates roughly to "The People's Pools," and the name tells you something important: this is a place Icelanders have been coming to bathe and explore for centuries. It remains the most visited destination in the entire interior -- and for good reason.
What hits you first is the color. The mountains here are made of rhyolite, a silica-rich volcanic rock that weathers into extraordinary shades of pink, rust, green, yellow, and purple. The most famous of these is Brennisteinsalda -- "Sulphur Wave" -- a roughly 855-meter peak that looks like it was painted by someone who couldn't decide on a palette. Iron creates the reds, sulfur the yellows, copper the greens, and silica the pale whites.
Then there's the hot spring. A natural geothermal stream flows into a cool brook at the edge of the lava field, creating a bathing area where the water hovers around 36-40 C. It's free, it's open whenever you can get here, and there's nothing commercial about it -- just a river of warm water in the middle of a volcanic wilderness. Soap and shampoo are prohibited to protect the ecosystem.
The surrounding Laugahraun lava field is an obsidian-black flow from a 1477 eruption, still looking fresh after five centuries. Walking across it feels like stepping onto another planet.