Tucked away amid the black lava landscape just south of Reykjavik is Iceland’s most extraordinary geothermal pool, the Blue Lagoon. An ethereal milky-blue lake, it is fed by naturally heated and mineral-rich seawater. Just the sight of its steaming blue expanse is enough to justify its ranking in our list, but for the full experience, you’ll need to jump in and smother yourself in the white silica mud. There are also spa facilities on hand, from waterfall-powered hydraulic massage to steam rooms.
