Diest is a commune of 22,000 on the Demer river, 20 kilometers west of Hasselt. It is the northeasternmost municipality in the Hageland region; beyond Diest lies the Kempen. Diest's monuments are comparatively intact by war-torn Belgian standards. The Beguine Convent is one of the largest in Belgium. The town square is surrounded by a number of historically interesting architectural specimens, including the Town Hall, the Church of St. Sulpitius and St. Dionysius, and several private residences. For centuries, Diest was ruled by nobles from the House of Orange, to whom several of the town's public facilites previously belonged, including the Warande Stadspark and a picturesque watermill.
The E14 roadway passes through Diest from east to west.
Deurne, Kaggevinne, Molenstede, Schaffen, and Webbekom are boroughs within the municipal district of Diest.