The four sites of the prop­er­ty form a strip 170&nbsp,km long by 3&ndash15&nbspkm wide, cross­ing Bel­gium from east to west, con­sist­ing of the best-pre­served 19th- and 20th-cen­­tu­ry coal-min­ing sites of the coun­try. It fea­tures exam­ples of the utopi­an archi­tec­ture from the ear­ly peri­ods of the indus­tri­al era in Europe with­in a high­ly inte­grat­ed, indus­tri­al and urban ensem­ble, notably the Grand-Hor­nu col­liery and workers&rsquo city designed by Bruno Renard in the first half of the 19th cen­tu­ry. Bois-du-Luc includes numer­ous build­ings erect­ed from 1838 to 1909 and one of Europe&rsquos old­est col­lieries dat­ing back to the late 17th cen­tu­ry. While Wal­lo­nia had hun­dreds of col­lieries, most have lost their infra­struc­ture, while the four com­po­nents of the list­ed site retain a high mea­sure of integri­ty.