Retreat Spa at Blue Lagoon

The Retreat Spa sits inside a lava field at Grindavík on Iceland's Reykjanes peninsula, built directly into the rock beside the Blue Lagoon's silica-blue geothermal water. Unlike the main Blue Lagoon next door, access here is restricted to guests of The Retreat hotel and to day-spa visitors who book the dedicated Retreat Spa package, keeping the underground treatment rooms and private lagoon corners quiet. The spa's signature is its subterranean cave setting: treatment suites carved into the lava rock combine massage and facials with direct views of or entry into the mineral-rich water. Signature treatments draw on the lagoon's own silica mud and algae, used in body wraps and facials administered by therapists trained in geothermal spa therapy alongside classical Swedish and deep-tissue massage technique. Facilities include a private in-lagoon relaxation area reserved for spa and hotel guests, a steam cave, an ice hut for cold therapy, and a dedicated lounge with juice and light food service. Booking is by reservation only, with treatment times and lagoon access sold as combined packages rather than walk-in slots; guests select from a printed treatment menu covering massage duration and facial type at check-in. The Retreat's spa is positioned as Iceland's most exclusive geothermal experience, reflecting the country's tradition of lava-field bathing while adding a five-star hotel layer of privacy and personal service rarely found at Iceland's larger public lagoons.