Tindoul de la Vayssière, Natural pit cave in Salles-la-Source, France.

Tindoul de la Vayssière is a natural pit cave featuring an oval-shaped opening about 40 meters long and 25 meters wide. The shaft descends about 67 meters into limestone, with an extensive network of passages extending more than 2 kilometers below.

Exploration began in the 18th century, when the abbé Charles Carnus and his team descended to the bottom of the shaft. In summer 1892 Édouard-Alfred Martel explored it with his cousin Gaupillat, and in 1962 Francis Maurette and R. Veyrunes carried out the first reconnaissance. Louis Armand later installed a metal staircase, and in August 1949 Louis Balsan photographed a dry gallery he called his masterpiece.

The generic name tindoul comes from an Occitan onomatopoeia for the sound of stones thrown into a well, echoing back up. Related local terms for wells and chasms include tintarelle, tombarelle and donde, whose root dod- recalls a bell struck by a falling stone. The word tindoul itself simply means aven or gouffre in Occitan.

The pit opens directly in the rock face with no marked path or railing at the rim; the metal staircase Louis Armand installed serves cavers inside, not casual visitors. The main gallery runs about 4 km, but two or three galleries remain inaccessible. Access to the interior requires caving experience and equipment.

An underground river system beneath the pit connects to the waterfalls of Salles-la-Source through intricate limestone channels. This hidden water flow feeds the springs visible above ground, linking the hidden depths to the landscape people see every day.