The Afsluitdijk is a 20-mile dam that has been protecting the low-lying Netherlands from the force of the ocean for decades. According to Daan Roosegaarde, a Dutch artist who works in urban environments, it’s quite famous in the country because “basically, it protects us from drowning.”

Roosegaarde recently installed the “Gates on Light” on 60 massive floodgates split between both ends of the dike. Because of sea level rise, the structure is in need of renovation. Roosegaarde wanted to use this opportunity to draw attention to the importance of the dam—which many take for granted—as well as to another environmental issue: light pollution.

According to the World Atlas of Artificial Night Sky Brightness, more than 80 percent of the planet’s people, and 99 percent of the populations of the United States and Europe, look up to skies so polluted with light that the Milky Way is virtually invisible. Amsterdam’s skies are some of the most light-polluted in the world.

Roosegaarde said that when Dutch Ministry of Infrastructure commissioned his firm to “sort of enhance the beauty of this 32-kilometer line” he wanted to do something “with light, with energy.” But they knew this would be a challenge, because of the way the elements—salt, rain, wind—would ruin anything too delicate.

They landed on a futuristic, energy-saving design inspired by the retroreflective wings of butterflies. When cars drive by the floodgates, their headlights illuminate the reflective material, thus using an already-present light source to brighten up the gates without an external source of power. When the car passes, the gates go dark again.


“It’s a statement about landscape,” said Roosegaarde, “which is energy-neutral. There’s only light when cars are there, so there’s no light pollution. It feels like a gateway to how a new world can look.”

Studio Roosegaarde, Roosegaarde’s firm, has two more projects planned for Afsluitdijk that deal with climate change and energy. The second one is an exhibit in a bunker near the dike that uses uses bioluminescent algae to create electricity-free lighting and highlight the power of nature. The third project uses electricity generated by the wind to power glow-in-the-dark kites and kite lines. The installation is also meant to demonstrate a new way of producing clean energy, and apparently can generate enough electricity to power 200 Dutch homes.

Correction: An earlier version of this post stated that 80 percent of the planet’s land area experiences light pollution. We meant to say 80 percent of the planet’s people do. The spelling of Daan Roosegaarde’s name has also been corrected.