Suomenlinna is a popular historical fortress island just a 10 minute ferry ride off the Helsinki Market Square. It has an excellent brewery bar, nice cafes, sunny fields and old fortress walls with rusty cannons lurking out from the gun holes.
It has a small beach, too. But although this small family-friendly shallow cove is very charming, especially in September when the cooling water drives all the tourists and kids away, I prefer the rocks.
Suomenlinna’s rocks and cliffs are perfect for a summery picnic and swimming. You just need some patience to find the right spot and you really need to know how to swim. And also be super careful with your steps, and if you jump, and where you jump!
Some foolhardy daredevils are known to jump from the fortress walls into the channel that’s steep and deep enough for passing cruise liners. Don’t do it.
Take sharp turn over the bridge to the right, that’s where locals live and swim, or follow the herd and look some of the Suomenlinna sights as you look for a spot. Two years ago I found an abandoned piece of scaffolding from a cliff that was turned into a swimming ladder. That has been my favorite spot ever since.