Fort Nieuwersluis still holds a Cold War command post

From the road, Fort Nieuwersluis can look like a quiet green mound. The revealing story sits behind brickwork and pressure-resistant doors. The nineteenth-century New Dutch Waterline planned to stop an enemy by deliberately inundating carefully chosen land. Decades later, part of the fort became a 1965 civil-defence command post that could be sealed during biological, chemical or nuclear danger. A guide links the old telephone exchange, diesel emergency generator, ventilation system and wall maps to those two very different ideas of national protection. This is not primarily a castle-photo stop; its value is seeing how Dutch water geography shaped military engineering, and why a fort that never fought a battle can still explain public fear and preparation. For 22 August, adults pay €10 or €7 as members; children up to twelve pay €5 or €3. 50 as members. Natuurmonumenten requires at least four tickets per booking, otherwise the tour may be cancelled and refunded.

• The tour takes place on 22 August 2026.
• Adults pay €10 and children up to twelve €5; members receive a discount.
• A minimum booking of four tickets applies.
• The fort is cold; dogs are excluded and accessibility varies by section.

Hokimi field note: Bring a layer even on a warm day. Before booking, check the four-ticket minimum, children’s tolerance for enclosed rooms and any mobility needs. A companion who prefers daylight can combine the visit with a walk and the fort café instead.

Information verified on 21 August 2026 · Source1 · Source2