Around 1870, the artificial grotto made from thermal stones with the drinking fountain was built along with the Friedrichsbad. It is fed by the Fettquelle where the water reaches temperatures of up to 63°.
The Fettquelle which originates from the south-east slope of the Florentinerberg is one of the twelve historical thermal springs in Baden-Baden. The “fette Quelle”, as it was already referred to in 1606, emerges from the monastery church “zum Heiligen Grab” and provided the bathing inn “Zum Ungemach” situated there with hot water until the end of the 17th century.