Forest Lagoon is a modern geothermal spa tucked into a small forested setting in North Iceland, ideal for a restorative soak after a day of sightseeing. You should book a time slot in advance, bring swimwear and a towel since rentals can be limited, and plan on staying about one to two hours; showers are required before entering and lockers are available. The water is comfortably warm, around 36 to 40 Celsius, so expect a relaxing, slightly mineral feel and keep valuables out of the pools. It’s car-accessible and makes a great evening stop for a chance to see the northern lights in winter, but expect more visitors in peak season. It is a bit expensive, but we thought it was worth it. There are several pools, cold dip, sauna and steam room.