Stoomtrein Katwijk-Leiden is a narrow-gauge heritage railway beside the Valkenburgse Meer, just outside Leiden. Steam and diesel trains run on a short lakeside line, and the site also includes the National Narrow-Gauge Railway Museum.
It is best for railway enthusiasts and families with children, but the small scale is part of the charm. Check operating days before going, since heritage trains usually run on limited schedules rather than as a daily attraction.