On the coast of Helsinki, Finland lies a sea fortress so large it spans over a cluster of seven rocky islands. Enjoy peacefully walking through the ancient fortifications without the interruption of cars zooming around. The ever-changing owners of the fortress combined with the various styles of architecture make this UNESCO World Heritage Site the perfect place to spend the day while traveling in Finland.

Now known as Suomenlinna, this fortress has had other names. It was built by the Swedes as a base for the Archipelago Fleet to protect against the Russian Empire and was then known as “Viapori.” Construction began in 1748 and lasted more than 40 years, but the fortress was never truly finished. However, 200 buildings and over three and a half miles of defensive walls were built.

The Swedish were able to maintain control until 1808, when the Russians were able to gain access. The Russian Imperial Government made grand plans for the fortress and expanded the perimeter to include Santahamina, Kuningassaari and Vallisaari. They built barracks and an Orthodox garrison church, but their rule was also destined to end.

By 1918, the newfound Finnish government took over and renamed the fortress the Castle of Finland, or Suomenlinna. Today, the castle and grounds are a tourist hotspot and picnic lover’s haven. The area is best explored on foot for the day. Wear comfortable shoes and get ready to go on a journey through history. The main route through the fortress is called the “blue route” and runs north to south through the main sights.

Begin your adventure at the main quay in front of the Jelly Barracks and end at the King’s Gate. Your journey will last about a mile and is clearly marked with blue signs. Read signs along the way that document the history of the area. The signs will give insight into the Russian merchant’s quarters, the Church Park, the fortifications of Kustaanmiekka and more. Note that the streets have no names. Instead, the addresses go by a letter designated to each island and a house number. The islands are lettered as such: A = Kustaanmiekka, B = Susisaari, C = Iso Mustasaari, D = Pikku Mustasaari and E = Länsi-Mustasaari.

The end of the blue route is particularly interesting, as here you will find old bunkers, canons and perfect picnic spots where you can look at the fortress wall ruins. King’s Gate was built from 1753 - 1754 and had a double drawbridge. Other sights on the islands include the museums. One particularly interesting museum is Ehrensvärd-Museo, which was once the home of Augustin Ehrensvärd, designer of the fortress. Outside of the museum, you’ll find Viaporin Telakka, a shipyard that has been active with sailmakers and other workers since the 1750s. Don’t miss seeing the last surviving Finnish submarine, Vesikko, while there.

The fortress is open daily except for Good Friday, Independence Day (Dec. 6), Christmas Eve and Christmas Day (Dec. 24 - 25). Ferries go back and forth and take about 15 minutes from the passenger quay at Kauppatori. Start planning your adventure to this amazing landscape of military history today!