Trou qui Fume - Parc van Furfooz

It is a natural vertical shaft or well, connected to the underground course of the Lesse .

During severe frost, warm air escapes from the shaft, creating a mysterious "puff of smoke" – hence the name "smoking cave." This phenomenon occurs because the temperature of the underground water is higher than the outside air, causing vapor to rise and even ice formations to appear in front of the cave entrance.

In the Middle Ages, people believed the smoke came from the Earth's core —sometimes associating it with hell or ghosts. In warmer periods, the cave is often inconspicuous , with no visible vapor or smoke, but the system behind it extends deep and wide beneath the park . Unique moss species and bats that thrive in the humid microclimate live in and around the cave—making it a small ecological hotspot .

At freezing temperatures , icicles or icicle flowers sometimes form around the entrance because the rising steam freezes — unique in Belgium!

It is part of the underground Lesse and is connected to other caves such as the Trou des Nutons and Puits des Vaux.

Willem Vandenameele