Ice Hotels · 4

Jukkasjarvi lies above the Arctic Circle, beside the Torne River, and the winter there is long and dark. Ice forms thick enough on the river to be cut and moved. A structure made of that material cannot last past the thaw, and nothing built from it can be treated as permanent.

Since 1989 the winter building has been raised again each season from river ice and snow, and taken back by the river when it melts. Walls, vaults and furniture are cut from the same material, and each season's rooms are carved by different hands, so the plan is not repeated. A separate year-round part was later built and is kept cold by other means.

The building is low and white and hard to read as architecture from outside. Inside, the surfaces are translucent, the light comes through the walls rather than from windows, and every sound is absorbed by ice and snow.

Alta lies in Finnmark, far north in Norway, where the river valley freezes hard and daylight is short in midwinter. Snow and ice are the materials most easily to hand, and both disappear in spring. Anything raised from them is a seasonal structure, standing on ground that will be bare again.

The igloo hotel is built again for each winter beside the Alta River, from snow packed into vaults and ice cut into walls, beds and carved surfaces. The plan changes from one season to the next because the whole structure is new work. Permanent buildings on the same site take everything that cannot be made of snow, so the ice part stays purely a shell.

Outside there is a rounded white shape in a valley of snow. Inside the corridors are curved and low, the carving changes from one winter to the next, and the walls give off a faint blue light.

Kemi stands on the shore of the Gulf of Bothnia, where the sea itself freezes and snow lies deep from early winter. The shoreline is flat and exposed, with wind coming off the ice. Snow is available in quantity, but only for part of the year, and the site returns to open ground each spring.

Rather than a single building, the snow is used to make a walled castle with towers, courtyards and thick outer walls that hold off the wind. Inside those walls sit rooms, a restaurant and a chapel, all cut from snow and ice. The whole thing is designed anew and rebuilt each winter, so the layout and the towers are never quite the same.

From the shore it stands up as a white wall with towers, which is unusual for a building made of snow. You pass through a gate into a courtyard, and the sea ice begins a short distance behind it.

The site is high in the Bernese Oberland, on open mountain ground above Gstaad. There is no road to the door and no permanent building to work from. Snow is what the mountain provides each winter, and it will not carry a heavy structure or survive the first warm weeks of spring.

Instead of one large hall, the plan is a group of separate domes joined by short passages, because a dome carries its own load in snow. The village is packed by hand each winter and left to melt at the end of the season. Sleeping, eating and gathering are put in different domes, and everything sits directly on the mountain surface.

You arrive on foot or on snow, and the domes appear as low white mounds on the slope. Between them you are outside again, in the open air of the mountain, before ducking back through the next low entrance.