The Creux Bleu is a site for underwater caving... and picnics! This resurgence, which is prolonged by a short canal flowing into the Ignon, offers a mysterious view of a cave connected to the largest underground network in Burgundy (Combe aux Prêtres de Francheville). The hollow owes its name to the rare colour of the water which comes from microscopic algae characteristic of underground waters. The site was built in the 12th century by Lord Othon de Saulx to supply water to a mill.
The washhouse located on the canal near the bridge leading to the car park dates from the 19th century. It has the particularity of having a mobile floor whose position adapts to the variations of the water level.
The landscaped surroundings of the Creux Bleu make it a pleasant place to picnic. It is also the starting point of a 9.5km marked trail, the Creux Bleu Trail in Mortière.
You will discover a unique natural site "le Creux Bleu" (blue hollow), a high place of the French Resistance and a natural heritage. "le Creux Bleu" comes from a subterranean river from Francheville. The site was fitted out in the 12th century and the hollow was explored for the first time in 1973. This blue color is due to the chemical properties of the stone or to the microscopic blue seaweeds on the rock.