How an eerie 40-mile cave system has remained a mystery for 8,000 years

The 40-mile cave system continues to baffle scientists even to this dayA cave system in France was first explored by humans 8,000 years ago but how they entered remains a mystery to scientists.The 40-mile-long subterranean Saint-Marcel cave system near Avignon, in France, was occupied by humans but questions remain as to how they carried out the journey.Even modern day well-equipped explorers struggle to overcome obstacles in deeper parts of the caves.Equipment like powerful lights, high-tech sa