The castle and hamlet of Eternes, in the municipality of Saix in the Loudunois has a water spring which was once famous for its healing power and was credited by popular belief with the privilege of being eternal.

A fountain by the name of Saint Martha has now been replaced by a small chapel inside the castle property.

Long ago, this spring was visited by people with eye disease, mostly ophthalmia. They washed their eyes with the valuable water and with it they filled small bottles to continue with the treatment at their homes.