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.