A ride on Föri, a ferry for pedestrians, is a must if you are with children in Turku. It only takes a minute to cross the river and the ferry goes non-stop. The views are not bad for adults either, especially during a regatta. The pics are from the Gangut regatta (31.7-3.8.2014).
On the harbour side of the river there is also a playground and an ice cream booth close to the jetty, just to make the location even more tempting.