Snorralaug

Located in the tiny Icelandic village of Reykholt, the beautiful little hot spring known as Snorralaug is thought to have been used by locals since the 12th century, making it possibly the oldest human-used hot spring in the country.

The quaint little hot spring is first mentioned in the medieval writings of Snorri Sturluson, a poet, and politician whose work has made him a famous artisan even today. According to his writings, Sturluson used the naturally heated pool to bathe. Sturluson lived nearby and even had his own private tunnel that led from his home directly to the foot of the hot spring.

While it is likely not how it looked in Sturluson's time, today the pool is surrounded by a circle of flat flagstones, and a quaint stone patio that runs right up to the green burms around the hot spring. There is also a door set into the squat hill behind the pool that leads to Sturluson's private tunnel, which can be investigated by curious visitors. Of course this door does nothing to discourage the spring's fantastical look. 

The temperature of the hot spring is said to fluctuate drastically, often becoming far too hot to bath in. Should this be the case, Reykholt also has a library that is focused on Sturluson's work, so while it's not a dip in a hot spring from Middle Earth, if you can read Icelandic it may be just as relaxing of an experience.