Now converted into a cultural and tourism centre, the Mills of the Dukes of Arenberg were built in the late 14th century on the banks of the Senne. The main watermill today includes impressive machinery (powered by a paddle wheel 7.5m in diameter), the Porphyry Museum and temporary exhibitions. As well as talking about these paving stones known all over the world as ‘Belgian blocks’, we look back at the history of porphyry, the Quenast quarries and the hard labour of the ‘Cayoteux’, the name given to the quarry workers. Among other things you can learn about the different types of stone and the tools used at the time.