With its main chamber about thirty metres deep, its stalactites and its pools, the cave of Saint Vincent opens into the unknown underground world. It was formed by the dissolution of limestone from the Carixian period (Lower Jurassic period) by atmospheric water, loaded with carbon dioxide, which infiltrated the rock. This erosion gives rise to a karst landscape (a landscape of sinkholes, sinking streams, caves, springs). Although this cave is less of a mystery to geologists today, it has long been the site of a legend.

According to tradition, it was here that Saint Vincent, a 4th century priest who came from Africa with Saint Domnin and Saint Marcellin to preach the Christian message in Provence, came to pray.  Renowned for his gifts as a healer and teacher of the Christian faith, he infuriated the Devil, who decided to lock him up in the cave to starve him to death.

But Saint Vincent overcame the devil and changed him into a 5-metre long stone serpent. The authors of the 19th century saw in the different formations and shapes of the cave significant elements of the Saint's life: the well where he took his water, the oven where he baked his bread, the fire-place where he heated himself... and the trace of his foot - the so-called "piayo" - which he imprinted in the ground by holding back the rock with which the Devil tried to obstruct the cave.

Until the beginning of the 20th century, there was a small chapel outside where the inhabitants of Melan village came in procession on Trinity Sunday.