On 14 August 1965, the village of Uudenkylä, near the southern Finnish city of Lahti, saw one of the worst peacetime disasters in Finnish military history. A network of underground tunnels and bunkers, built 40 years previously in the village to store ammunition for the Finnish Defence Forces, suffered an enormous explosion, leading to 4 fatalities and 69 people injured, many severely.
The exact cause of the explosion was never discovered. According to reports from the time, the most likely cause was a stone falling onto a crate of ammunition. But as a result, all similar storage facilities around Finland were immediately taken out of military use and no longer used for ammunition storage. One such facility had just been built in the countryside outside the city of Pori, on the west coast of Finland, but in the aftermath of the Uudenkylä tragedy, it was never actually used for its original purpose and subsequently lay empty.
Sixty years passed. After being used for everything from potato storage to winter pétanque practice, the Pori tunnel facility came to the attention of a newly established company called Ficolo. As the name suggests, Ficolo was set up with the aim of bringing the co-location hosting model to Finland for the first time, replacing the on-premises model that then prevailed among the country’s businesses. While at present the Finnish data centre market is concentrated around the Helsinki region (Google’s gigantic Hamina facility, soon to receive over a billion dollars of investment for waste heat re-use, is 150km to the east of the capital), when Ficolo started out the idea was that location mattered less to clients.
This meant Pori as a location fitted the bill. And when the tunnel complex came up for sale among a batch of ex-government owned assets, Ficolo, now known as data centre provider Verne, took the plunge and bought it. The result was Pori Data Center, an 11MW, 8,500 sqm data centre spread across nine independent tunnel halls – with a built-in advantage for sustainability.
“Being underground, the Pori facility sits at eight degrees Celsius all year round – you get all the cooling from Mother Nature,” Kim Gunnelius, Head of Finland at Verne, told Capacity. “That makes it optimal from a power perspective. At the time we opened the centre, sustainability was perhaps not as important an issue as it is now, but we decided to go all in on this aspect anyway.” The Pori facility’s green credentials also come from its power supply, which makes use of the abundant wind power availability on the western Finnish coast. There is also a solar plant covering 2,600 sqm of the centre’s roof space.
With the tunnel structure, power and utility supply, and access routes all already in place, converting the complex to data centre standards did not take long, and the facility was ready for occupation after around six months of construction. At the time, there was nothing like the squeeze on labour and materials there is now in the data centre build market. “Back then, if you would have thrown people at it and have everything ready up front, you could do a project in six months. Now, you can’t even get diesel generators in six months,” said Gunnelius.
From a technical standpoint, most of the conversion work focused on constructing the cement floor, as well as waterproofing and structural work to the roof of the tunnels. Other work on the centre included fitting direct liquid cooling for the racks (shown above). Along with the tunnels’ natural low temperature, this helped push design PUE down to 1.16x in optimal conditions.
Of the hundred or so clients who have rack space at Pori, several chose the site because of the security it offers. Thanks to its previous life as a military facility, the complex is easy to restrict access to, and biometric access control, multiple security zones and universal HDCCTV help to back up these architectural security advantages. Another growth area for Pori, Gunnelius says, is AI. It is well reported that the growth in AI compute means latency is less of a factor, and by extension this means facilities in alternative markets can capitalise on AI demand. “The capacity demand is much greater than it has ever been. And the size of the cases is really big as well. You could easily sign a contract to fill a whole 100 MW facility with just one customer. To meet the demand, we are planning to invest significantly and have strong financial backing to do so.”
The one disadvantage of the underground location, however, is that unless heavy mining machinery is involved, you can’t really expand. This means that the centre’s customers are limited in the amount of space they can take in the same rack location if a contiguous space is on the shopping list. However, western Finland in general is a potential growth area for Verne as a whole. The climate-based advantages of a Nordic location, as well as stable and largely renewable grid availability, means the firm’s clients are looking for more space in the region to capitalise on future AI-driven demand, and western Finland fits the bill alongside the Helsinki region – but the new facilities are likely to be above ground this time.
The conclusion? If you’re looking for a secure data centre location with a stable, year-round climate, it’s worth seeing if any old bunkers are going spare.
