Identifying the underground cavities in inhabited areas is an important issue for BRGM. In this video, discover the mysteries of the underground galleries of Orléans.
28 January 2022

What’s going on under our feet, under the centre of Orléans?

At a depth of around ten metres, in the bowels of the earth beneath the city of Orléans, numerous galleries have been dug by people since the 11th century. What can be found there? Are there any risks? We explain everything.

© BRGM

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In Orléans, as in many cities between the 10th  and the early 20th century, many galleries were dug to extract stone for the construction of buildings.

After being mined for stone, several of them were put to other uses. For example, from the 19th to the middle of the 20th century, the Orléans quarries were used to grow Belgian endive because of the ideal growing conditions (darkness, temperature and constant humidity).

The underground quarries of Orléans also played a role during the 2nd World War. To protect the inhabitants from bombing, the city’s cellars and quarries were hastily fitted out to accommodate up to several hundred people.

Over time, many of the city's former quarries have been abandoned and roots and water infiltration increase the risk of collapse. These situations are a serious threat to public safety, especially when they occur in city centres.

BRGM’s role

One of BRGM’s tasks is to find and inspect these cavities to prevent collapses. Using new technologies, our specialists can detect cavities from the ground surface or scan them in 3D to determine their size and the position of unstable areas in relation to buildings on the surface.