Source Bleue du Château de Dortan

The spring takes the form of a flooded shaft 4 metres in diameter. At the bottom of this shaft, 20 metres deep, a restriction (for a laden diver) opens onto a chamber with a low point at -26 m. The passage's cross-section decreases and, after a low point at -80 m, exploration was temporarily halted because of the current.

Exploration was temporarily halted because of the current.

At the entrance to the chamber, a line gives access to small passages in the ceiling. The main line rises to a large boulder at -16 m. The passage then takes a steep downward slope (an over-deepened phreatic conduit), down to -40 m. At this depth, the passage turns to the right and becomes much less steep. A long straight section follows, up to a squeeze at -60 m. The continuation was seen by Jean-Jacques Bollanz and Luigi Casati. The dives at the end of 2010 made it possible to progress to 1030 metres from the entrance, at a depth of 99 metres.