Each day fresh water bubbles up from the spa's subterranean grotto, which is 55m under this Norwegian beach hotel in Larvik.
Step on board the Vulkana at Tromsø, an old Norwegian fishing boat, for an Arctic spa with a twist. The boat has a salt-water hot tub, plus a Finnish sauna and Turkish steam bath.
The Salt Creek Spa at the Ystad Saltsjöbad hotel in Skåne, Sweden, has a beautiful coastline. There is an indoor ice hole to jump into post sauna and a warm low-tide pool.
