Perched on the edge of the Atlantic in Kopavogur, a short hop from central Reykjavik, Sky Lagoon is a geothermal spa built for slow, restorative soaking. The infinity edge dissolves into the sea, so you float in the steaming water while the horizon and, on winter nights, the northern lights stretch out before you. The Pure Pass includes the seven-step Skjol ritual, a Nordic sequence of hot pool, cold plunge, sauna, mist and body scrub. Book a sunset slot for the loveliest light, and arrive early to settle in without rushing.