Frequently Asked Questions

Useful information

The answers to the frequently asked questions can be found here and find the Bunker Day Survival Guide underneath! Is your question not listed? Please contact us via the contact box.

General information

The new date for 2023 will be announced soon.

During Bunker Day, the remains, such as bunkers and other elements of the Atlantic Wall along the coast of The Netherlands, are put in the spotlight and opened to the public for one day. Sometimes the bunkers are still clearly visible and accessible, but sometimes also overgrown by nature or located on a private area. During Bunker Day, we make locations accessible and we organize additional educational activities such as guided tours, film screenings and re-enactment.

Bunker Day is originated in 2014 due to the desire to extend the scope of the (mostly local) initiatives and activities that exist around the Atlantic Wall heritage and to stimulate cooperation between these parties. And that worked! Bunker Day now comprises more than 25 organizations, 110 bunkers from the Wadden Islands to the border of Belgium and attracts more than 15,000 visitors every year.

The European Heritage Atlantic Wall Foundation is the initiator of the Bunker Day. The organization is done by Donkergroen creators.

Thousands of varying sized bunkers were built at a high rate as part of the Atlantic Wall during the occupation. After the war they were quickly abandoned, demolished, buried under the sand (from the dunes) or otherwise left to become derelict, allowing nature to slowly take over.

Bats in bunkers

It has mainly been bats that have discovered the benefits of safe and frost-free winters in bunkers. The fact that most of the concrete constructions were subterranean meant that they were ideal locations for breeding and shelter during wintertime, providing a safe ‘meeting place’ for male and female bats.

Bats are the only mammals that can fly. Thanks to their special way of life, they can reach a great age, individuals frequently passing 30 years of age. Food for these insect-eaters is scarce in wintertime and so it is essential that they can count on undisturbed shelter for the colder months. Properly maintained bunkers can serve as their dwelling for years.

Of the approximately 20 species, it is mainly the Daubenton’s bat, the lake bat, the whiskered bat and the common long-eared bat that use the Atlantic Wall bunkers and corridors. It is important that the locations used by these species remain undisturbed from August to mid-May (their winter and breeding season).

A bunker must meet a number of standards:

  • The climate inside the shelter must remain constant i.e. frost-free in winter.
  • It should be sufficiently moist so that the bats do not become dehydrated.
  • Any predators should be kept out.
  • Humans should not disturb the shelter.

The preservation of cultural heritage bunkers goes hand-in-hand perfectly with the preservation and expansion of winter shelters for bats, amphibians and insects.

Want to find out more about bats? Check either of these websites: and/or

Please contact us via the box below. 



Remaining questions? Don’t hesitate to contact us!

Bunker Day Survival Guide

Wear suitable shoes

By suitable, we mean sturdy shoes that are good for walking through loose sand and mud. There is a small amount of water on the ground in some of the locations so it's handy if your shoes are waterproof too.

Wear suitable clothing

It's not a good idea to wear your Sunday best to Bunker Day. Some visits require a bit of climbing and clambering before you can get to the location. Loose-fitting clothes make this easier, of course. Additionally, many of the locations have been untouched for some time, resulting in rather dusty interiors. The dust may transfer to your clothes if you happen to brush up against something.

Be on the alert for ticks!

Bunker Day is held during tick season and we hope that the weather will be favourable. Please watch out for ticks if you have exposed skin while walking through high grass, bushes or wooded areas. Long trousers and long-sleeved shirts are recommended. It's even a good idea to tuck your trousers into your socks.

Don't forget your torch

Some of the bunkers haven't been lit since WWII. We do our best to make sure each location has lighting but even then, there are still many dark corners, hallways and rooms that you may want to explore, so make sure to bring a torch!

Watch your step

Bunkers consists of irregularities at unexpected places, holes or, for example, cable ducts. So be careful where you walk! And also be careful of protruding pieces of concrete or iron.

Be kind

Bunkerdag is possible because of the volunteers and crew members. They guide you, share information with you and they will make sure you are experiencing the best Bunker Day ever. Be kind to these amazing humans.

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