Grottes de Remouchamps, Natural cave system in Aywaille, Belgium.

Grottes de Remouchamps is a cave system in Belgian limestone featuring multiple chambers with stalactites, stalagmites, and underground waterways. The network extends several kilometers beneath the surface with varied passages for exploration.

The caves were discovered in 1828 and opened to the public in 1912, when visitors were given smoking torches for light; permanent electric lighting followed in 1924. During the Second World War the galleries served as a refuge for the inhabitants of Remouchamps. The first chamber had already been frequented 8,000 years ago by Mesolithic hunters.

The caves are nicknamed the "Merveille des Merveilles" and are a major tourist site in the province of Liège and Wallonia. During the Second World War they served as a refuge for the people of Remouchamps. A small museum and thematic exhibitions stand at the exit.

Visitors can join guided tours lasting about 75 minutes that include both walking sections and boat journeys through the passages. Guides provide explanations in French, Dutch, English, and German.

The lower gallery's boat trip covers 600 metres, described in the sources as the longest underground navigation in the world. The flat-bottomed boats pass the Palmier, a column formed where a stalactite and stalagmite have joined, and the ceiling dips low in places. The only animals here are small unpigmented shrimps, the niphargus.