A short ferry ride across the bay from Helsinki, Suomenlinna makes for a pleasant excursion from the Finnish capital.
Apart from the many fortifications there is quite a lot to see on the island, or, more correctly, islands as Suomenlinna is spread across 3 or 4 closely connected islands, joined by bridges.
Inside the fortifications there's a tranquil world of duck ponds, quaint houses, little inlets with boats and yachts moored and lighthouses. It's all very rural and a far cry from the city a few minutes away.
The views back across the bay to the city are worth the trip too.
I did find that the best views of the islands are from the Helsinki - Tallinn ferry that sails very close to the iconic, Kings Gate, the main entrance to the old military fort.
Not much more to add, not a destination that would warrant a purposeful trip but something to do if you are in the vicinity.