Abisko is a national park in the far north of Sweden, 195 kilometres inside the Arctic Circle, and its fame rests on a hole in the cloud. Atlantic air off the Norwegian coast has to cross the border peaks first, and leaves most of its moisture there. What comes down over Abisko and Lake Torneträsk is dry, so a clear patch a few tens of kilometres wide hangs over the park, on far more nights than the aurora towns across the mountains get. Locals call it the blue hole. Most people arrive by train, on the iron-ore line that runs past it. The valley view is closed by Lapporten, a broad U glaciers cut between two peaks: the Lapp gate in Swedish, Čuonjávággi, the valley of the geese, in Sami. From here the Kungsleden, the King's Trail, runs 440 kilometres south through the fells, and a day on its first stretch carries you through birch forest and tundra past the turquoise Abiskojåkka canyon. Around midsummer the sun never sets, and the trail can be walked at any hour.
Away from the station lights, out on the frozen surface of Torneträsk or on a dark rise above it, nothing stands between you and the sky. A chairlift climbs Mount Nuolja to the Aurora Sky Station, a lookout 900 metres up, clear of the valley lights. Sami families, whose reindeer still move across this ground, keep the wait warm inside a lavvu, their cone of poles and canvas, a fire in it and reindeer hide underfoot. You step out into the cold whenever the sky flares, and duck back in when it fades. It can go quiet for an hour at a time, and the cold, not the cloud, ends most nights. When it comes, a faint green arc swells into curtains of green and violet that slide overhead, the mountains black against the stars. The blue hole only buys you a sky you can see through. The rest is waiting, in and out of the tent, until you push the canvas aside and it has already begun.