Seljavallalaug Pool in Iceland is the oldest swimming pool in the country, built in 1923. It's about 20 minutes to hike there from the parking lot and it's free, however the pool has lukewarm temperature compared to regular hot springs. That means you won't probably stay in there for longer than 15 minutes. On the other hand it is a pretty cool experience and place for photos when its not busy.

• Expect dirty changing rooms.