Aven d'Orgnac is a large karst cave system located in the Ardeche region of France, approximately 25 kilometers northwest of the town of Vallon-Pont-d'Arc. The cave was discovered in 1935 and has since become a popular tourist destination, known for its impressive array of stalactites, stalagmites, and other geological formations.

Visitors to Aven d'Orgnac can take a guided tour of the cave, which lasts around 75 minutes and covers a distance of approximately 1.5 kilometers. During the tour, visitors will pass through several large chambers and galleries, each with its own unique formations and features. One of the highlights of the cave is the "Grand Stalactite", a towering column of calcite measuring over 30 meters in height.

In addition to the cave itself, Aven d'Orgnac also features a visitor center and museum, which provides information about the geology and history of the cave, as well as the surrounding Ardeche region. The museum also features exhibits on prehistoric life in the region, including the famous Chauvet Cave, which contains some of the oldest known cave art in the world.