If you see only one place in Helsinki in the summer, you could make it Suomenlinna .The “Gibraltar of the North” was once the greatest sea fortress in the Baltic, built by the Swedish in the mid-1700s at great expense to protect their eastern flank. But when the Russians invaded in February 1808, the bulk of the unprepared and bankrupt Swedish army hastily withdrew, allowing the Russians to conquer Helsinki without a fight and besiege the fortress. With no reinforcements in sight, commander Carl Olof Cronstedt surrendered unconditionally two months later, and Finland was ceded to the Russians. Cronstedt’s actions probably saved countless civilian lives, but King Gustav IV needed a scapegoat and sentenced him to death for treason; fortunately, the losing king was himself soon overthrown, and Cronstedt lived out his years gardening.
Today’s Suomenlinna is still living in its own time with only old buildings, few cars, fewer than a thousand inhabitants and lots of old fortifications, catacombs and cast iron cannons. But it’s not just a museum: the sprawling complex houses restaurants, cafes, theaters and museums, and is a very popular place for a picnic on a fine summer day, watching the vast passenger ferries drift by on their way to Estonia and St Petersburg. It was included in UNESCO’s World Heritage List in 1991 as a unique monument to European military architecture.