In the area near Saumur called Anjou, along the Loire river, huge layers of soft sandstone, tufa, and limestone are found, It is rather easy to carve out holes, houses and whole cities. Several small caves were formed by the Loire and have already been used by prehistoric man. But most of caves found today are artificial, the oldest of these "caves" were originally quarries. The people needed the stones to build houses, churches and monuments. They often followed the layers of a specific stone, so after some time, the open quarry became a sort of mine, a subterranean quarry. Sometimes, the people used those quarries later for other purposes, like cellars, storage rooms or houses.
Cave houses have several advantages to other houses: they are cheaper, warm in winter, cool in summer. When a cave is built for living, the stone can be sold to reduce the cost. In central Europe they have a temperature of about 10°:C, which is rather cool, but may be easier to heat in winter than houses with thin and not isolated walls. Most cave houses in this area are also a matter of culture, it was common to build cave houses, so maybe nobody really thought about an alternative.
There are two importants kinds of rock in the area, le tuffeau (tufa) which was formed by the deposition of limestone from limestone rich water. It is rather young, porous and soft, at least while underground and humid. Cut into blocks it becomes dry and hard, light and a good insulator. This is an ideal rock for building houses. The second rock is le falun (shelly sand), a limestone rich in shells which was deposited about 12 Million years ago. It is found more or less only around Doué la Fontaine.
Most tourists know the area along the Loire river for its Renaissance castles, the Loire châteaux. Most of those castles were built during the 17th century during the reign of Louis XIV.. The construction of so many castles created an urgent demand for stones. This made the quarries profitable and increased the tufa and falun quarrying. The area is also a wine-growing region called the Touraine. Wines from this region are generally of high quality and elegance. Many former quarries were converted into wine cellars during the centuries.