A tower at Aarschot beach. Evidence of an ancient sea.

The Sint-Rochus tower is the only remnant, and probably even the bell tower, of the former cloth hall. The gothic tower was built around 1300 in iron sandstone and is thus a clear example of the popularity of this type of stone in that period for official buildings. In 1719, the city built a new town hall against the Sint-Rochus tower, which has since served as a secure storage place for the municipal charter of freedoms and other important municipal archival materials. Until 1794, the tower sometimes served as a prison, torture, and hostage room. It was certainly white plastered in the 19th century. In 1920, the destroyed town hall was demolished, leaving the tower standing free. The building was then used for a long time as a police station and as an office for the tourism department. The tower was fitted out in 2005 as a medieval donjon, although it has never been one.

To what extent the appearance of the tower is still influenced by the original structure, we do not know. What is remarkable is that almost everything here – even the tracery windows – is made of iron sandstone and that no other type of stone than iron sandstone was used. If you walk around the tower for a moment, you will see almost all the phenomena we discussed earlier in this walk: weathering, iron concretions, goethite, restoration mortars, holes from mason bees, and charred strikes.

At the bottom, you see stones with worm-like figures. You have probably seen these in other places with iron sandstone and wondered what they are. These are burrows of beach worms and evidence that the substrate finds its origin in a marine environment. These beach worms must have been very active here. While alive, the walls of the burrows were reinforced with deposited slime. Afterwards, these burrows were filled with sand and fossilized during the soil process.

Jan Rymenams