The Retreat at Blue Lagoon Iceland

The Retreat is built into a lava flow that hardened some eight centuries ago, its sixty suites arranged so that the volcanic rock comes right up to the glass. Guests have exclusive use of a private section of the Blue Lagoon, reached directly from the spa, away from the day visitors.

The spa itself is largely underground, carved into the lava, with a sequence of rooms for the silica and algae rituals, a relaxation lagoon and in-water treatments. The Moss restaurant, set into the rock above, serves tasting menus built on Icelandic ingredients.

Keflavík airport is around twenty minutes away and Reykjavík about fifty, which makes it a common first or last stop on an Icelandic trip rather than a base for exploring.