The Vianden Pumped Storage Plant sits a few kilometres north of town, built into the hillside above the Our river. It is one of the largest pumped-storage hydroelectric facilities in Europe, with a visitor centre that explains how the plant works and why pumped storage is increasingly important for balancing electricity grids as renewable generation grows.
The facility is run by SEO (Société Electrique de l'Our) and guided tours can be arranged. The powerhouse itself is built underground in a large cavern inside the hill. Even if you have limited interest in engineering, the scale of the installation inside the mountain is impressive.