The Eyserbeek is a small river flowing through the southern Dutch province of Limburg, winding its way from its source near Bocholtz through the villages of Simpelveld and Eys before emptying into the river Geul near Gulpen. As a right-bank tributary of the Geul — itself a tributary of the Meuse, which ultimately drains to the North Sea — the Eyserbeek is part of one of the most ecologically significant river systems in the Netherlands. The stream passes through a charming rural and historic landscape, flowing past the monumental Oude Molen and Bulkemsmolen watermills (built in 1774 and 1753 respectively), and through the heart of Simpelveld, where a 2012 town square renovation uncovered the previously culverted river and created a new bluestone riverbank. The Eyserbeek sits between the plateau of Bocholtz to the south and the plateau of Ubachsberg to the north, giving it a gentle valley character typical of South Limburg's rolling terrain. It eventually meets the Geul near the site of the former Motte-and-bailey castle Gracht Burggraaf in Gulpen, at the same confluence where the Gulp River joins from the opposite bank.