The Neptune Caves (French : Grottes de Neptune), also known as the Grottes de l'Adugeoir are a series of natural caves located in Wallonia near Petigny in the municipality of Couvin, Belgium. They are located on the Eau Noire river, a tributary of the Meuse.
Many of the chambers are accessible to the public via a guided tour, partially via boat on the underground river. [1] [2]
50°3′57.73″N4°30′43.32″E / 50.0660361°N 4.5120333°E