Mossy Fountain, Thermal fountain in Cours Mirabeau, Aix-en-Provence, France

The Fontaine d'eau chaude, also called fontaine moussue, stands at the top of Cours Mirabeau in Aix-en-Provence. Its original structure is hidden under a limestone deposit formed by the 18 °C thermal water, which feeds mosses, ferns and algae. The visible mass is a rounded rock draped in green, sitting in an octagonal grey stone basin with a moulded rim and a shallow pool.

The fountain was built in 1667 on Cours Mirabeau and tapped into the warm underground Bagniers spring flowing beneath the street. It was originally designed as a thermal water source and has served residents as a natural water point since its creation.

Locals call it fontaine moussue, the mossy fountain, though Aix has several. Until the early 20th century women came to wash linen here, and buckets were drawn for scrubbing doorsteps and stairways of neighbouring buildings; in the exceptional winter of 1985, with pipes frozen, it was one of the few public water points still running. A plaque beside it recounts its history.

The fountain is centrally located on Cours Mirabeau and remains accessible 24 hours a day without any entrance fee. It is best visited on warmer days or in the early evening when more activity fills the area.

The scholar Émile Lèbre identified three moss species, a filamentous alga and several diatoms on the stone. In the exceptional winter of 1985, when many pipes froze, this fountain was one of the few public running-water points in the city and residents carried water home as in the past.