On June 18, 1646, shepherds discovered a "bright spring" in the Mühltal valley and immediately reported it to the mayor. He visited the spring, drank its water and washed himself with it. A few days later, he discovered that he had been cured of his ailment, pain in his hips.

According to chroniclers, other illnesses such as open wounds, aching limbs, broken bones and poor hearing were also treated. Word of the healing powers of this water spread quickly, so that many people hoped for relief from their ailments every day.

The bathing and spa business reached its peak in the years 1696-1700. Ducal instructions ordered the expansion of these springs, two fountain diggers were employed and several buildings were erected near the springs. In 1697, the Duke appointed a town and country physicist to look after the bathers. The baths became extremely busy for the time. It is said that up to 1,000 people drank from the healing waters every day.

It is recorded that a "café house" was opened in Rastenberg as early as 1696, which is all the more astonishing when you consider that coffee had only been introduced to Germany a few years earlier.

Two fountain houses in Mühltal, in the immediate vicinity of the forest swimming pool, are reminiscent of this time.