Jukkasjärvi, Sweden
Icehotel
The original, rebuilt annually beside the Torne River since the late 1980s, now with a year-round ice wing alongside it.
Ice harvested from the Torne in spring is stored through the summer and used to build a new hotel each winter, with art suites designed by a different set of invited artists every season — carved, lit and furnished individually, so the building is effectively a group exhibition you sleep inside. Alongside it, Icehotel 365 stays open all year, cooled by solar power in the Swedish summer, which is a genuinely strange and clever piece of engineering.
As a hotel it is more capable than its reputation suggests. Warm chalets and rooms provide the base accommodation, there is a proper restaurant working with northern Swedish produce, and the sauna and hot-drink routine around a cold night is well drilled. The village of Jukkasjärvi is small; Kiruna and its airport are close, which makes reaching it easier than the latitude implies.
The surrounding programme — dog sledding, river trips, guided aurora nights — is a substantial part of what guests actually do. If the northern lights are the reason for the trip, treat them as weather rather than an amenity, and give yourself several nights.