The Neolithic flint mines of Spiennes, located near Mons in Belgium, are a testament to prehistoric engineering and cultural progress. Active between 4,300 and 2,200 BC, these mines are recognized for their impressive size and the variety of extraction techniques employed by Neolithic people. The site, which covers over 100 hectares, was added to UNESCO's World Heritage List in 2000 for its cultural significance and its demonstration of early technological innovation.