On the menu today: Perhaps no other city in the world has done more to prepare for being bombed than Helsinki. What started as a response to hard lessons from the bombing of Finland’s cities in World War II by the Soviets accelerated through the era of nuclear fears of the Cold War, and continues to this day and demonstrates a particularly Finnish approach to how you protect your citizens from aerial bombardment. Join me for a walk through one of the largest and most complex underground structures in the world.
A Teeming Network of Underground Bomb Shelters
Helsinki, Finland — In the downtown of this capital city, just off Hakaniemi Market Square, the entrance to Arena Center Hakaniemi could easily be mistaken for an elevator and stairway to an underground parking garage. In fact, the underground complex does include a parking garage — alongside a gym, several youth soccer courts, and a whole lot else.
But the stairs go deep — eight flights, and each landing of each flight is made of metal grates, creating the unnerving sense that you can see all the way down, beneath your shoes.
But there’s a purpose to this flooring, even if it’s no friend to any user unnerved by looking down from a great height. If some sort of terrible explosion occurred at the entrance to the stairs, some of the concussive force from the blast would pass through the flooring of the stairway landings, hopefully keeping the stairway intact.
Arena Center Hakaniemi is part of a vast network of underground civil defense shelters.
Yesterday’s newsletter briefly discussed Finland’s Winter War and Continuation War against the Soviet Union. A lot of countries saw their cities bombed during World War II. But the effect of seeing Helsinki and other major Finnish cities bombed by the Soviet Air Force — and the crowded, limited underground bomb shelters sometimes running out of room for terrified civilians — left a deep and lasting scar on the Finns’ sense of what was needed to protect all of their citizens. After the war, the Finns decided that if bombs ever fell on their cities again, everyone in the country would have access to an underground shelter.
The result is more than 50,000 civil defense shelters across the country, with space for 4.8 million people, which is almost sufficient for the population of 5.5 million people. The shelters underneath Helsinki collectively have room for 940,000 people; the city has about 700,000 residents.
As Atlas Obscura puts it, “No Finnish government official would ever mention Russia as the reason for such defensive preparations, but they don’t have to.”)
While many of these bunkers were built during the Cold War, the construction of mandatory shelters in new buildings is still a standard requirement in Finland. Residences or workplaces, or any building above 1,200 square meters that is permanently occupied, must have a shelter, as must any industrial building more than 1,500 square meters. The construction cost is not subsidized and must be covered by the owner of the building.
Once you get to the bottom of Arena Center Hakaniemi, you are greeted by two large doors. Our guide, Civil Defense Planning Officer Jukka-Pekka Schroderus, explains that the first massive and thick steel door is to protect anyone inside the shelter from any explosive blast wave; the second is to protect those inside from chemicals, potential biological weapons or toxins, gases, or radiation.
Schroderus explains that the shelters are largely built under streets, so that if a building above it were to take a direct hit, it is unlikely to cause a collapse into the shelters underneath.
Our footsteps echoed through tunnels wide enough to drive a car, under fluorescent lights. The walls are designed to absorb heat; if, in a crisis, the shelters would become crowded, and the temperature would rise.
The underground shelters are built with ventilation, autonomous water supply, and air filtration systems. The shelters do not have stored food; Finns are expected to have a “go bag” with proof of identity (although it’s not required to enter the shelter), food, personal medication, and hygienic supplies for up to three days. Finnish civil defense authorities also recommend sleeping bags, flashlights and batteries, and iodine tablets. Alcohol is not permitted, which is probably wise but disappointing. In any circumstance where I would need to hastily evacuate to a vast underground shelter, I could probably use a drink.
The grim outlook for Helsinki cats and dogs is that pets are not allowed.
Now, here’s what makes the Helsinki shelters particularly surreal: They’re used all the time for other non-emergency activities. As mentioned above, Arena Center Hakaniemi has gyms and indoor soccer fields, as well as a kids’ bounce house and a snack bar. Other underground shelters have pools. The Finnish authorities hope that they will have 72 hours to prepare the shelters for emergency protective use — draining the pools, removing extraneous equipment, etc.
Schroderus explained that it was important that civilians use the shelters for non-emergency purposes on a regular basis for several reasons. First, regular use exposes maintenance issues — leaks in the ceiling, lights that have burned out, etc. Second, in case of an emergency, Finns will already be familiar with the nearby underground complexes.
Here’s another surprising fact about the Helsinki underground shelters: According to our guides, they’ve never been used in an actual emergency.
As extensive and expensive as Finland’s underground network may seem, foreign leaders are now looking to see if they can learn a thing or two from the Finnish endeavor.
Back in March 2025, Ukrainian President Volodymyr Zelensky and Finnish President Alexander Stubb visited Merihaka, the city’s largest civil protection shelter, built in 2003.
We live in a world where not only do drone attacks regularly send citizens of cities in Ukraine and Israel into the nearest bomb shelter, but cosmopolitan and once seemingly safe cities like Dubai, Doha, and Abu Dhabi have found themselves experiencing missile and drone attacks. In Operation Spider Web in 2025, Ukraine deployed hundreds of drones that had been covertly smuggled into Russia and launched from hidden compartments inside cargo trucks. Every defense and homeland security agency around the world looked at that and realized how many sites in their country were largely or fully defenseless against a threat like that.
Now imagine instead of drones being deployed from mundane-looking civilian trucks, your favorite city faced the threat of a drone factory working out of a shipping container.
Later in the day, my group of American journalists visited the Finnish technology firm Sensofusion, which manufactures anti-drone weapons — jammers, as well as smaller, faster drones that deploy in small groups and intercept and down incoming drones. Sensofusion’s CEO and founder, Tuomas Rasila, told us his company wanted to develop the best anti-drone defense systems but had no interest in building weapons to kill human beings.
One of Sensofusion’s ideas in the works is a “Tactical Drone Factory,” which the company touts as a “fully self-contained drone manufacturing facility built inside a standard shipping container. Equipped with industrial 3D printers, an electronics assembly station, and a complete parts inventory, a single Drone Factory can produce approximately 50 interceptor drones per day. The factory can be operated by a small team and deployed anywhere in the world.”
Now, Sensofusion may not want to create drones that kill people, but there are likely some bad people in this world who would like to create their own anonymous-looking shipping containers that can pump out 50 drones a day, and after a few weeks, launch hundreds of drones against some unsuspecting target.
The day that happens, every city in the world will wish they had a vast network of underground civil defense shelters the way Helsinki does.
ADDENDUM: In response to Monday’s edition, some readers wanted to know if Finland was pulling its weight in terms of its contributions to NATO.
This year, Finland will spend $7.6 billion, or 2.5 percent of its gross domestic product, on defense — a 5 percent increase from the amount of spending last year. They expect to reach 3.2 percent of GDP by 2030, which would bring the country closer to NATO’s target of 3.5 percent by 2035. (I was going to say something snarky about Spain, but they did hit 2 percent for the first time since 1994.)
Here’s what Finland probably doesn’t get enough credit for: It’s one of just ten NATO members that have mandatory conscription. Every Finnish male serves six months, nine months, or a year depending upon his chosen role, and after returning to civilian life, he remains in the reserves. This means Finland “can mobilize about 280,000 troops for wartime service, backed by a reserve of roughly 900,000 citizens. In a nation of 5.6 million, nearly one in six people has military training and can be called up if needed. . . . Finland is moving to raise the maximum reservist age from 60 to 65, a change that would add about 125,000 people and push the total reserve closer to one million by 2031.”
In addition to a lot of potential manpower, Finland brought at least two strengths to NATO that the U.S. and the rest of the alliance desperately needed: The first is exceptional cold weather forces well-trained and prepared for warfare around the Arctic Circle and above it, and the other is a world-class fleet of icebreakers; “80 percent of the world’s icebreakers are designed by Finnish firms and more than 60 percent of icebreakers are built in Finnish shipyards. This hard-earned knowledge has made Finland a global authority in the icebreaker industry, and it now seeks to share its know-how via the ICE Pact — a trilateral partnership between the United States, Canada, and Finland.”