In the 18th century, monks from nearby Stavelot’s abbey created an oxbow lake on the Amblève by digging a short-cut river channel at the tiny hamlet of Coo (pronounced 'Koe'). Cascading 15m, this forms Belgium’s tallest 'waterfall'. It's no Niagara, but cupped in a pretty woodland valley, the scene is charming at dusk once the hordes of amusement-park day trippers have gone home. Coo is also a usefully accessible starting point for all manner of outdoors activities.