Dasht-e Lut holds the hottest ground temperature ever recorded on Earth: 80.8 degrees Celsius, caught by satellite over its dark, stony surface in 2018. That is the ground baking rather than the air, well past the 70.7 degrees once logged here in 2005. The desert sprawls across roughly 51,800 square kilometres of south-eastern Iran, and in 2016 it became the country's first natural UNESCO World Heritage Site. Its western edge is filled with kaluts — parallel earth ridges that a relentless summer wind, holding the same line for thousands of years, has carved from soft sediment. Some stand as tall as a 50-storey building and run unbroken for more than 40 kilometres, together the most extensive field of their kind anywhere. Walk between them and the gaps look like straight streets running between walls of earth, which is why the kalut field is so often described as a city. Far east, the Rig-e Yalan sand sea heaps dunes up to 475 metres high, among the tallest on the planet.
For years the Lut was assumed to be lifeless, and its scorched heart nearly is — almost nothing survives around Gandom Beryan, the black lava plateau where those records were set. At the cooler margins, though, foxes, sand cats, lizards and stubborn shrubs hold on, so the desert is more empty than dead. Its finest hours come after sunset. As the light drops, the kaluts glow copper and their long shadows stripe the sand; then, with no lamp for a hundred kilometres in any direction, the sky clears until the Milky Way spills from horizon to horizon. Travellers come mainly in spring or autumn, entering from the small town of Shahdad on the western rim, since summer here is genuinely dangerous. They camp among the ridges to feel heat, silence and open sky in something close to their purest form.