The Secret Lagoon in Flúðir dates back to the oldest swimming pool in Iceland. It was originally built in 1891 and used water from a hot spring. "Gamla laugin" was used for swimming lessons from 1909 to 1947, but slowly fell into oblivion after the construction of a new pool.
After a change of ownership, the new owner intensely pursued the idea of renovating the bathroom and reopening it. The pool has been completely cleaned and renovated, but has otherwise remained in its original form. It is built of natural stones and surrounded by hot springs, the bottom is made of small pebbles. Even today, the bath is supplied directly from hot springs and the water is not chlorinated. A modern bathhouse with changing rooms and a cafe completes the complex. The water has a temperature of 38 to 40 degrees Celsius all year round.
A small highlight is the mini geyser right next to the bath. It erupts about every 5 minutes and its fountain is a good two meters high.