Thousands of people in France used to live underground in caves and one region has one of the richest collections of troglodytic sites in Europe.
As early as the 5th century, tunnels were carved into the rock – first to dig out the stone and later, in the 18th century until as late as the 1950s, to make homes.
In the 18th century, of the 4,000 inhabitants of the town of Doué-la-Fontaine near Saumur, Maine-et-Loire, half are thought to have lived underground.
There are an estimated 1,500km of galleries, cellars and former habitations in an area of nearly 600km² – although the majority are no longer accessible.
The oldest site open to visitors with evidence of human activity going back 1,500 years is Troglodytes et Sarcophages, Doué-en-Anjou.
It is classified as a historic monument and is looked after by Didier Chabot.
He said: “In our region, the troglodytic sites are not natural caves formed by geology and so were not lived in by prehistoric man. Instead, they are openings and tunnels created later in two local rock types which are fairly soft and easy to dig into.
“By the side of the Loire river there is a local type of limestone called tuffeau and here the troglodyte activity is known as du coteau, meaning galleries were dug into the hillside. It is where the stone for the famous Loire chateaux was extracted.
“In the area where I am, the stone is falun, for which there is no exact translation. It is a sandy, friable rock full of shells, formed 10 to 15million years ago when sea covered the land.
“Here, the troglodyte activity is known as de plaine, where people dug down from the flat plains to create a large open pit.
“From the bottom, they would start digging horizontally into the rock. It is extraordinary. Everything was done by hand with picks. They would have needed pulleys to move cut rock out of the way.”
The Troglodytes et Sarcophages site was first explored by archaeologist Michel Cousin 27 years ago. He spent five years examining galleries running through a hectare of land.
He discovered that, in the 5th century, the rock was used to make tombs, found in churches as far away as Normandy and Brittany, and there is a possibility they were taken across the Channel to the UK.
It is estimated that 25,000 were made here. “It was the period of Clovis, the first king of the Franks, who converted to Catholicism, which led to the development of Christianity,” said Mr Chabot.
“The tombs were 2m long and weighed around 500kg when they were finished.
“It must have been a mammoth task to pull them out into the open and then up to the plain above. They would have been transported by river and sea to get to their furthest destinations. You can still see where they were worked underground.”
The second use was as a refuge from war from the 8th century onwards. They would have been a safe haven when the Vikings headed up the Loire in the 9th century.
“A 12th-century text witnesses that in the 11th century people from Saint-Hilaire- Saint-Florent hid underground from attackers from Normandy.”
Another discovery was a chamber with Roman and Gothic arches, showing it was most likely created as a chapel during the 12th century.There are niches carved in the rock face, which it is thought would have held statues. Above was a chateau, which has since disappeared, but the lord who lived there must have found the underground space perfect for worship.
There is also evidence that some of the underground area might have been used as a farm during the Middle Ages as there are traces of a dovecote and places where animals might have been kept.
However, these caves were not used later on for housing, as was common in other underground complexes. Instead, it was used as a quarry for building stone.
The workers would start digging from the top and, as they moved downwards, they would open out, creating a vaulted ceiling which would keep the structure solid and avoid collapse. It makes these chambers look like a cathedral.
Later, the site was used by a winemaker and it was not until Mr Cousin visited and started exploring the tunnels stretching back underground that its full history was revealed.
Elsewhere in the region, people started creating underground dwellings in the 18th century. “People were poor, and they would dig down into the plain to create a courtyard,” Mr Chabot said. “From there, they could dig into the rock to make a room with alcoves for beds and cupboards.
“Usually, the family would live in one room and the animals in others. They would use some of the stone they dug out to create supporting arches inside and walls at the front.
“There would be a fireplace and a chimney which, for people walking across the countryside above, was the only sign someone was living below. The advantage was a constant temperature of around 14C throughout the year. The disadvantage was lack of light and high humidity, and lung disease was common.
“The dwellings are not rich with detail because they were simple homes carved out of the rock for the poor but they are our own specific architecture with no equivalent anywhere else in France.”
After World War Two, as living conditions improved and there was more modern housing available, the dwellings began to be abandoned.
Some continued to be used for wine cellars and by mushroom-growers.
Recently, they have been rediscovered. Some have been restored and renovated to include modern comforts and turned into homes once again, or even unusual restaurants, chambres d’hôtes and hotels.
There are also other museums to visit. Maisons Troglodytes de Forges, between Saumur and Doué-la-Fontaine, shows how a 19th century family would have lived in their house carved into the rock.
The village of Rochemenier has two old farms, with dwellings and outbuildings, consisting of 20 rooms over five acres and an underground chapel.