Geologically remarkable spring that rises directly from the sandstone rock in a cave.
The name has been documented since 1327 and commemorates the Irish monk Pirmin († 753), founder of the Reichenau monastery and patron saint of the old Pfungen parish church. According to tradition, he stayed in the area and is said to have settled temporarily at this or a neighboring spring.
Support for the cave ceiling and access rebuilt in 1975 by the city of Winterthur.