The river Lesse has carved out these chalky rocks through the ages, creating numerous caves and sink-holes. 

The most spectacular of these karstic phenomena is the underground arm of the Lesse, which crosses the entire rocky hill chain, creating a whole world of underground rooms, galleries and a lake. 

The many caves and caverns have been occupied by man for thousands of years (-14,000 approx.) and are still inhabited today by bats! This rich archaeological heritage is home to many objects witnessing man's presence over the years. 

In more recent times, a fortress and baths were built here at the end of the Roman era, although only their ruins remain today. However, the ancient spa was entirely rebuilt in 1958 and is well worth a visit. 

Nature-lovers will also enjoy the many chalky lawns naturally mown by sheep - a genuine paradise for observing the local insects and orchids.