COUVIN, just 5km south from Mariembourg, was one of the first settlements in Hainaut to be industrialized, its narrow streets choked by forges and smelting works as early as the eighteenth century. In the event, Couvin was soon marginalized by the big cities further north, but it has battled gainfully on as a pint-sized manufacturing centre. Tourism has also had an impact, as the town lies at the heart of a popular holiday area, a quiet rural district whose forests and farmland are liberally sprinkled with country cottages and second homes. Long and slim, and bisected by the River Eau Noire, Couvin is short on specific sights, but it does possess a good-looking if small old quarter, set on top of a rocky hill high above the river and main road, where you’ll find the boringly modern main square, place du Général Piron. About 3km north of town, in a lovely spot that’s difficult to reach without your own transport, tours of the Grottes de Neptune (whttp://www.grottesdeneptune.be) last an hour and take you part of the way by boat on an underground river, before wowing you with some typically dramatic music and light shows.