In the south-West of France, the limestone uplands stretch in a broad band from La Rochelle to Montauban. Only the eastern part of this band, bordering on the foothills of the Massif Central, offers many visitable caves.
It forms a semi-circle from Brive to the Massif de la Grésigne near Albi, traversed from east to west by the valleys of the Vézère, the Dordogne, the Célé, the Lot and the Aveyron. Here there are two large regions of karst.
One is the Perigord, formed of limestone from the upper Cretaceous period overlaid by sands and of Palaeogene clays, consisting of:
- Perigord Blanc, around Périgueux drained by the river Isle
- Perigord Noir further south drained by the Vézère and the Dordogne The other is the Quercy formed of limestone from the middle and upper Jurassic, which contains:
- The Causse de Martel between the Vézère and the Dordogne
- The Causse de Gramat between the Dordogne and the Lot
- The Causse de Limogne between the Lot and the Aveyron
Because they consist of quite thin layers of limestones and are not very high, the Causses of the Perigord and of the Quercy, as well as being well karstified, contain many drowned systems and sinking streams (known locally as “igues”) and resurgences are frequent
At the same time, the valleys which cut through the ancient systems, have made access to the caverns easier by increasing the points of entrance.
The prehistoric inhabitants took shelter in many caves, which they enriched with an archaeological and cultural heritage which has led to the Valley of the Vézère being called the Valley of Mankind.
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