Going for a swim is probably not the first thing visitors to Iceland think to do, but seeing the lovely, historic Seljavallalaug pool might change their minds. 

Built in 1923, Seljavallalaug may be the oldest swimming pool in the entire country. It was created as a place where locals could learn to swim. Though many of them subsisted off the fishing industry, there was no formal place for them to develop their swimming skills. In modern Iceland, swimming training is mandatory in public schools, a trend that began with facilities such as Seljavallalaug.

The 82-foot-long pool is built right into the rocks, in a shallow valley created by a pair of verdant, craggy hills. Until 1936, the remote swimming hole was the largest pool in Iceland. It is fed by a nearby hot spring that usually keeps the water at a temperature above freezing, although in the winter, ice still forms on the surface. On the far end of the pool is a small changing room that provides some privacy. It is basic–don't expect showers–but does the job for those of a more modest nature.

Getting to the pool is an adventure in  itself. Visitors can drive fairly close to the secluded valley that holds the Seljavallalaug, but they must eventually park and set out on foot. The trek to the pool takes around 20 minutes of hiking through fields of lava ash, dodging little streams running out of the valley.

Seljavallalaug is not maintained in any official capacity but is cleaned once a year by a team of local volunteers. The waters are often covered in algae, and after the 2010 eruption of the Eyjafjallajökull volcano, ash. Yet no matter what is floating in the historic waters of the pool, its natural beauty makes even ash and algae easy to ignore.

The Atlas Obscura Podcast is a short, daily celebration of all the world's strange and wondrous places. Check out this episode about Seljavallalaug.