In Roman times, part of the cavity collapsed, covering and hiding the access to the galleries of the Font Major Cave for centuries afterwards. Throughout successive generations, the memory of the existence of this extensive subway cavity was forgotten, until it was rediscovered by the inhabitants of Espluga in the middle of the 19th century.

The rediscovery of the Font Major Cave took place on April 21, 1853, when the drilling of a well in a house in the village (the well of Cal Palletes) came across a lateral gallery leading to the subway river. An improvised expedition went up part of the subway river and also discovered the large galleries of the current entrance, which had been blocked by the aforementioned demolition and was partially filled in by sediments that had been deposited over the centuries. But it was not until August 28, 1956 when members of the Centro Excursionista Pirenaico went down the same shaft again and went through a good part of the galleries up to a first siphon that they could not flank.

A year later the current entrance was opened. From 1957 onwards, numerous explorations attempted to overcome the siphon, but it was not until one day in April 1957 when Diego Ciuraneta, a speleologist from the Tarragona Underwater Exploration Society, managed to cross it for the first time. Later, in 1965, two speleologists from the Speleological Research Team (ERE) went through it again and traversed 300 meters of totally flooded galleries. In 1985, a team from the ERE and the CEC resumed their studies of the Font Major karst.

The first siphon was crossed again and the subway river was traversed through totally unknown areas, until a second siphon was reached, which still could not be crossed. As part of this expedition: lakes, tunnels and several floors of fossilized galleries were carefully surveyed.