Waw an Namus is named for its mosquitoes, which should not be possible in open Sahara — and the insects are the giveaway that there is standing water out here, some 400 kilometres southeast of Sabha. It sits at the bottom of a volcano. The caldera runs about 4 kilometres wide and 100 metres deep, with a scoria cone 140 metres high at its centre and three small salt lakes curled around the cone's foot: one blue, one green, one rust-red, fed from below by springs and fringed with reeds and date palms. The eruption that dug it threw black basaltic ash 10 to 20 kilometres in every direction — roughly 300 square kilometres of dark desert on pale sand, plain enough to pick out from orbit. When it happened is unsettled: a lava bomb from the cone dates to about 200,000 years, yet the crater is so little eroded that some geologists read it as a few thousand.
The drive in crosses that ash: hours of flat black grit that muffles the tyres and hides what is coming. The crater gives nothing away until you reach the rim, and then the interior drops open below — reed beds, palms and water curved around a cone the colour of dry clay. Walk down and the dust smell goes, replaced by damp vegetation and warm, brackish water; coots and grebes clatter out of the reeds, and the mosquitoes find you fast. Getting here is still the hard part: southern Libya was effectively shut to visitors for more than a decade after 2011. That is changing, as an e-visa opened in 2024 and the Fezzan reopens to organised travel, but you cannot arrive alone. A licensed operator, a southern permit and a police escort are mandatory, routes are approved in advance, and permission can be withdrawn at short notice.