If you walked into this Finnish sports center, you’d probably notice the badminton courts, the boxing ring, maybe even someone squatting 600 pounds.

But what you wouldn’t notice? It’s built to survive a nuclear blast.

In this video from The WSJ, journalists travel to Finland’s Savilahti region to explore one of the country’s largest modern civil defense shelters: an underground facility carved directly into bedrock that can protect 7,000 people in the event of a chemical, biological, or nuclear attack.

And yes, it’s hiding in plain sight.

Forget the old-school image of a dusty concrete room with canned beans and a radio. Modern shelters, especially in Finland and Switzerland, are high-tech survival systems built with decades of evolving expertise. Finland alone maintains around 50,000 shelters, and they never stopped upgrading them after World War II. That “silent knowledge” has been passed down from generation to generation. These shelters are engineered so that even if something goes very, very wrong, they keep on working.

With Russia’s war in Ukraine raising security concerns across Europe, countries are reassessing civil defense infrastructure. While places like Germany and Sweden once had thousands of shelters, many were converted into apartments, galleries, or solar installations.

Rebuilding isn’t as simple as evicting tenants and dusting off old doors. Technology has evolved, threats have evolved, and that’s why manufacturers from other countries are visiting Finland: to learn from those who never stopped preparing.

A sports center by day. A blast-proof survival cave by night. Let’s just hope it always stays mostly about badminton. Watch below!