In the geological era between the jurassic and the chalk a limestone sedimentet in the this area. By this time there was an elevated land between the rivers "Ardèche" and "Cèze" as you can see in the picture. Both rivers were linked by a watersystem in the underground.
In the geological era of the Miocene the Mediterranean dryed out. That was about 5 million years ago. The implication of this process was the lowering of the ground water table of the surrounding.
As a consequence the Ardèche eroded deeper into the ground and the underground water system also lowered itself. So the caves build by the water in the karstic limestone dried out. As there was still a high grade of humidity in the underground dripstones emerged from the ceiling and the floor of the caves as water droppes from the ceiling always at the same place. So the chalk layers itself on the dripstones which makes them grow. They grow with a "speed" if 1mm per year. As the limestone contents lots of iron they get a red colour of the "rust".
The cave was discovered by Robert de Joly in 1935. As it is a karstic cave there is only a vertical natural entrance in opposite to the grottes which have a horizontal entrance.
Next to the entrance of the cave there is a prehistoric museum showing the life of the local people and the development of the cave.
All details about entrance fees, opening hours and guided tours you gather from this page: http://www.orgnac.com
We recommend doing a guided tour to see all the giganatic dripstones.
To log this earthcache you have to:
1.Take a picture of yourself and your GPSr at the entrance of the cave. This task is, recording to the guidelines, optionally.
2. Guess how high the ceiling is at the biggest hall of the cave.
3. Count the number of steps you have to decline to reach the big hall. 720 steps is not the correct answer. So we will not accept any logs with this number!
Send us your answers via GC-Mail. If they are correct we will give you the log-permission.
We hope you enjoy to visit the cave, which got a touristic award in 2004 to be one of the best presented touristic attractions in France.