Suomenlinna Sea Fortress, a World Heritage Site, off the coast of Helsinki, Finland is the perfect day trip destination. A half hour ferry ride from the port of Helsinki gets you there. (Make sure you sit on the top deck of the ferry, as the views of Helsinki as you head out of port are definitely worth the ferry ticket price)
The island, also know as Suomenlinna Sveaborg, has a wonderful tourist center and tour options, but it’s an amazing place to explore on your own. The open spaces as well as the older structures was a treasure trove of adventure for me!
The “island” consists of 8 small connected islands and thousands of nooks and crannies, fantastic ocean views and beautiful colors!
The history of Suomenlinna as a Fortress is equally impressive- Fortifications starting being built in 1748 and it was added to the UNESCO World Heritage List in 1991 because of its unique military architecture. The most impressive thing to me was the dry dock, which is still in use today. There weren’t many ships in, and some parts were under construction, when I visited, but seeing the raw “bones” allowed me to understand more about how it operated.