Halfway between Selvjalandfoss and Skógafoss waterfalls, there is an unmarked road that leads to a hidden and idyllic geothermal pool. From the pool's parking lot, you’ll have a 20-minute hike ahead of you along an unmarked trail, but you will eventually reach the pool—and I say pool because Seljavallalaug pool isn’t exactly a hot spring, it's more like a tepid spring. While not exactly cozy in the winter months, Seljavallalaug is a lovely hidden oasis in the spring and summertime.
If you're coming to Iceland, a bathing suit is a must--no matter the season. From the Blue Lagoon to public pools (Laugardaslaug in Reykjavik is really fun) and hot springs, there are plenty of opportunities to go for a swim. Seljavallalaug is one of Iceland's oldest pools, a quiet little place tucked away in a valley, but it involves a little bit of work. Located between Seljalandsfoss and Skogafoss off the Ring Road, to get to the pool you have drive down a bumpy side road, and then take a short 15-minute walk along the rocks and a few hops across the stream. All of the effort is worth it as you soak in your surroundings--it's just as peaceful as it looks. There's no attendant, but there is a small donation box for the wonderful volunteers who maintain the pool.