Saint-Marcel Network


Grotte Saint Marcel is the largest underground network in Ardèche and 4th largest in France with 64,2 kms of galleries currently mapped out. This colossal underground maze is under constant exploration.
Grotte Saint Marcel was discovered in 1836, but it wasn’t until 1892 that Edouard Alfred Martel started exploring the 2,260-meter long network, drawing up the first plans and sections.
Between 1931 and 1947, caving expert Robert de Joly resumed exploration of the network and went beyond the « Great Barrier » where earlier explorations had terminated. Under his supervision, the army blasted its way through the plug, opening up new galleries and extending the network to 3,260 meters.
In 1956, the Forez caving group carried on exploration and they were soon joined by other groups (the Brussels team, Courbis brothers, Lower Ardèche group …). Those years were full of discoveries as groups competed fiercely with one another. As a result, the length of galleries explored increased rapidly from 4,260 meters in 1953 to 24,757 metres in 1977.
  • saint marcel cave network topography E.A.Martel
As from the early 1990s, exploration carried on in both dry and submerged parts of Saint Marcel network. Ferdinand Meuret began diving in the flooded lower levels in 1966 and this exploration intensified with campaigns led by Philippe Brunet of the Avens Group or more recently by Pierre Baudu. The non-submerged network has also grown with the discovery of the Aven de Noël in 1990, the link with Deloly Cave in 2003 followed by Perte de la Cadière in 2005.
With two more recent discoveries (2019 – 2020) the total length of the network has extended beyond 64 kms of galleries as a result of the link between Saint Marcel network and Aven Noël cave plus 2 newly-discovered chambers right at the end of network 1 : the Salle du Rhinocéros and the Salle du Déconfinement.
Check out the televised news report on France 3’s « Faut Pas Rêver » programme and relive the discovery of the Salle du Rhinocéros as if you were there.
  • flooded galeries exploration network picture credit s rocheil 12 40
  • flooded galeries exploration network picture credit s rocheil 6 41
  • flooded galeries exploration network picture credit philippebrunet 42
  • salle du rhino network access picture credit g scherk 44
  • flooded galeries exploration network picture credit jp baudu 45
We now know that Saint Marcel’s network is organised on five levels, one above the other, with a total height difference of 325 meters (218m above the present-day level of the Ardèche river, and 107m below it).
That means that there are 3 upper « fossil » levels, sculpted out by the original underground river, and two still active but flooded levels, the deepest of which is 107m below the river Ardèche’s present level.
That makes it the longest submerged network in France with a total of 19 km underwater.
Eight different entrances are known today :
Two of them are man-made : the Visitors’s Entrance (191 m NGF/FOD; 147m above the Ardèche) and Aven Despeysse (224 m NGF/FOD, 180m above the Ardèche).
Five natural entrances : the historic « Natural Entrance » (87 m NGF/FOD, 43 m above the Ardèche), Grotte Deloly (57 m NGF/FOD, 13m above the Ardèche), La Perte de la Cadière (47 m NGF/FOD, 3 m above the Ardèche), Grotte du Bateau (49 m NGF/FOD, 5 m above the Ardèche), Source de l’Ecluse (44m NGF/FOD, at river level), and Aven Noël (262 m NGF/FOD, 218m above the Ardèche).