A ferry to the Suomenlinna fortress island runs about twice an hour, depending on the time of day, and costs EUR 2 one-way and EUR 3.60 round-trip. Ten-trip tickets issued for city public transport can be used on the ferry, too. From June to August, private water buses run from Kauppatori to Suomenlinna, charging EUR 3.50 one-way and EUR 5.50 round-trip.
Suomenlinna Ferry (0100-111).