Deep inside a labyrinthine cave in southwestern France, ancient humans who lived around 30,000 years ago carved horses, mammoths and rhinoceros into the walls, a fabulous prehistoric menagerie that has rarely been seen -- until now.

Discovered in 2000 by an amateur cave explorer, the Grotte de Cussac in the Dordogne department holds ancient human remains, traces of long-extinct bears and stunning, fragile artworks its custodians go to great lengths to preserve.

Typically, the French authorities restrict access to the cave to researchers, who are only allowed to enter it four weeks per year.

But a team of AFP journalists was recently allowed to visit the cave for the first time, accompanied by scientists working to unravel its mysteries.

After unlocking the metal grate that blocks the entrance, the group put on white protective overclothes, head coverings and gloves, then disinfected the soles of their boots.

Authorities are anxious to avoid a repeat of the damage done to France's famed Lascaux caves by microorganisms brought in by visitors.

The Lascaux caves -- which are also located in Dordogne, though their artworks are estimated to........

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