This cover from Belgium depicts a single stamp in 2022, celebrating the World Heritage Site Major Mining Sites of Wallonia. During the Industrial Revolution in the 19th century, mining and the heavy industry that relied on coal formed a major part of Belgium's economy. Most of this mining and industry took place in the sillon industriel, a strip of land running across the country where many of the largest cities in Wallonia are located. The Major Mining Sites of Wallonia is a UNESCO World Heritage Site comprising four sites in Wallonia in southern Belgium associated with the Belgian coal mining industry of the 19th and 20th centuries. The four sites of the grouping, situated in the French-speaking Hainaut Province and Liège Province, comprise Grand-Hornu, the Bois-du-Luc, the Bois du Cazier (showed in this stamp) and Blegny-Mine. The site was recognized by the UNESCO commission in 2012.