Near Port en Bessain in Normandy there is a river going underground surfacing not far from the port.?

The sinkhole is accessible according to a book I read on historical places in Normandy.What I want to know is if there are people who have been inside the cave system and can tell what it is like.

Hi from France (Brittany),

this is not "Port en Bessain", but "Port-en-Bessin" ... it's easier with the real name ...

I've found a web site with some information about this town, the river and the pits ... but it's a french site. This is my "translation" (I'm not fluent in English ... google translation seems to be intelligible).

Translation (helped with google) :

The river disappears thus under ground, entirely more than three quarters of the year, partly only during the time of the large rains. Water which cannot then be absorbed by the four pits forms a vast lake. Part of these lost waves reappears with seven hundred and eighty meters in straight line of the small pit of Soucy to form Aure lower, broad with its beginning of twelve meters with one meter of depth, new river which is thrown in the coastal river Transfers it. This new river runs at its beginning during three hundred and ninety seven meters then disappears during two hundred thirty-eight to reappear definitively then. Similar provision under ground occurs in the department for Muance, flow the Divine ones which, taking its source with Grainville-Lengannerie, disappears almost at once for ressourdre with Saint-Sylvain, after a course of eight kilometers. It is easy to give an approximate an account of the volume of water absorptive by the pits, Aure higher having a course of forty kilometers and Dromme, sixty; these two rivers receiving of many tributaries. The four pits are named Tourneresse, (forty-five meters on forty), Grippesulais, the Large one and the Small-Pit.

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However, I haven't found any article about expedition inside this cave ... it seems to be dangerous !

I hope these information helps you ...