With this card of Neolithic flint mines of Spiennes, sent by Gilles, i'm only missing 1 Unesco site from Belgium, the Lifts on the old Canal du Centre!!
The Neolithic flint mines of Spiennes are Europe's largest and earliest neolithic mines, located close to Walloon village of Spiennes, southeast of Mons, Belgium. The mines were active during the mid and late Neolithic (4400-3000 BC). The site and its surroundings were added to the UNESCO's list of World Heritage Sites in 2000.
It is well known for its flint mines, which are on the list of UNESCO World Heritage Sites since 2000. The entry on the list describes them as "the largest and earliest concentration of ancient mines in Europe" and cites the level of human technological development they demonstrate as justification for their inclusion.
The mines cover some 100 hectares of downland near Mons in Belgium and are interesting for showing the transition between opencast and underground mining for the flint nodules. The nodules were extracted using deer antler picks. The stones were then knapped into rough-out shapes of axes, and finally polished to achieve the final state.
The rough-outs were traded over a wide area, and were often polished at their destination. Polishing strengthens the final product, making the axe-head last longer. The axes were used initially for forest clearance during the early Neolithic period, and for shaping wood for structural applications, such as timber for huts and canoes. - in: wikipedia