> 19th August 1935
During a systematic exploration of caves south of the Ardeche gorges, a team of potholers led by a pioneering of speleology, Robert de Joly, arrived at the municipality of Orgnac l'Aven. The team was led to the natural entrance of the cave by villagers. The speleologists descended the 50 meter drop by rope ladder.
A series of amazing discoveries awaited them. Gigantic caverns and a fabulous array of formations, the most exceptional discovery ever made by Robert de Joly. The first expedition lasted 10 hours and enabled the explorer to judge the exceptional quality of the site. The first expedition lasted 10 hours and enabled the explorer to judge the exceptional quality of the site. That same evening, Robert de Joly called an extraordinary meeting of the village council since the caves were on municipal land and belonged to the village. The council rapidly decided to undertake work on the caves in order to facilitate visits. Robert de Joly became the technical advisor who planned and oversaw the work.

> 1938
Work began on an electrical generator installation for lighting the caves. The watchman's house was also built at this time. In the autumn, work started on a 105 metre long tunnel.

> 1939
The caves were opened to the public.

> 1954
The second chamber was fitted out, giving access to the final section, 120 metres below ground.

> 1965
A 50-metre, lift shaft was sunk ensuring easier access to and from the first chamber for the public.

> 5th august 1965
Guy Rieu and Jean-Claude Trébuchon, together with about thirty amateur speleologists, discovered new, imposing galleries increasing the size of the known network from 3 to 32 hectares (75 acres).

> 1988
The Regional Museum of Prehistory opened its doors. 1,500 square metres with three large exhibition rooms enabling visitors to discover the various prehistoric civilisations that developed in the Ardeche from 350,000 to 750 BC.

> 1996
The new project for the renovation and additions to the site were planned with the avid support of the local council. The first steps in the study began.

> 8th june 2000
The site was granted a listing and various institutions committed themselves to the project.

> October 2000
Work for a sum of €5,400,000 began in 3 stages:
- renovation and construction of a new visitor area to be included in an architecturally harmonious unit,
- lighting and pathways in the caves were refitted and improved,
- a 120-metre lift shaft was sunk enabling direct, easy return to the surface. par ascenseurs.

> February 2002
The work was finished, the Listed Site was opened.

> June 2004
The site is listed "label Grand Site de France®".