Visiting Suomenlinna Sea Fortress: Ferry, Tunnels and Island Walks

Guarding the sea approach to Helsinki across six linked islands just fifteen minutes off the harbour, Suomenlinna (known in Swedish as Sveaborg) is one of the largest maritime fortresses in the world and a UNESCO World Heritage site since 1991. Begun in 1748 by Swedish Field Marshal Augustin Ehrensvärd as a bastion fortress built directly out of local island granite to counter Russian naval expansion, it later served under Russian rule for a century before becoming independent Finland's coastal garrison in 1918. Today it is both an open-air historic park (with free admission to the islands and ramparts 365 days a year) and a living car-free neighbourhood of 800 permanent residents, artists' studios, cafés and breweries.

How to Take the Correct Ferry (Save Money with HSL)

At the eastern end of the Market Square (Kauppatori), two different boats sail to Suomenlinna. Always head to the white stone pavilion on the eastern quay (opposite the Presidential Palace) for the HSL Municipal Ferry (Suomenlinnan lautta), which runs year-round (even crashing through thick sea ice in January and February) every 20 to 40 minutes throughout the day at night. Because it is part of Helsinki's regular public transport system, it costs a standard HSL Zone AB ticket (or is included for free on a 24/48/72-hour HSL day pass). Private seasonal waterbuses departing nearby charge more than double the price.

Following the Blue Route from North to South (Allow 2.5 to 3 hours)

The ferry docks at the main jetty on the northern island of Iso Mustasaari. Follow the signposted 1.5-kilometre Blue Route spine south across bridges and causeways:

1. The Pink Jetty Barracks and Church: pass through the vaulted pink Tsarist-era jetty barracks to Suomenlinna Church, whose central tower still functions as a working air-and-sea lighthouse blinking four flashes in Morse code for the letter "H" (Helsinki).
2. The Great Courtyard (Suuri linnapiha) and Dry Dock: designed by Ehrensvärd in the 1760s around his own ornamental tomb, right beside one of Europe's oldest operational stone inner dry docks where historic wooden sailing ships are repaired.
3. Kustaanmiekka Bastions, Sandbank Earthen Mounds and the King's Gate: cross onto the southernmost island of Kustaanmiekka, where original 19th-century Russian coastal cannons sit atop grassy turf ramparts above dark stone casemate tunnels (bring a phone torch to walk through the unlit passages) leading down to the ceremonial marble-inscribed King's Gate (Kuninkaanportti, 1754) at the water's edge.
4. Submarine Vesikko and Toy Museum: in summer, climb inside the restored 1930s Finnish submarine Vesikko or stop for a homemade cinnamon bun in the veranda of Café Piper or Café Silo.