Just a 15 minutes boat trip from either Merisatama or Ruoholahti is excellent and small twin islands called Pihlajasaari. Islands have multiple beaches, restaurant, camping and even the nude beach!
It is a good place to go for a sunny day or for a whole weekend with a tent. There is said to be good fishing capes on the islands as well.
Between Pukinmäki and Pihlajamäki sits a park surrounded by vast grasslands for frisbee golf and football lovers. On the east side of it there is very amusing park for kids to play with several kinds of swings.
Nuorisopuisto is next to that and it is huge freestyle park for skaters, rollerblades and scooters. Park also boost a massive dirt track for BMX bikes with high jumps.
Even though you are not keen of doing mad jumps on ramps, the area is perfect for picnic and just watch people jumping and running around. If you dont want to be in the middle of it all, set yourself and basket far from everbody else on that huge and tranquil grass.
Helsinki has one real river and it`s ironically named by it`s neighbor city, Vantaa. Beside of that, river itself is very beautifull and it has been saved from housing developement, so on the both banks there is very good walking/biking tracks with excellent views to river.
River Vantaa runs to sea on Vanhankaupunginkoski and it goes all the way up to border of Vantaa about 10 km north from sea. Along the way there is pikkukoski beach, Tuomarinkylä-mansion restaurant, Haltiala consevation area and farm. It is very recommended Helsinki sightseeing every time of the year.
Just under a click north from Kauppatori market square, there lies a small island called Tervasaari. Alltough it is small, it still has restaurant and children playground on it. It is very beautifull spot to relax and have picnic.
On summer time Tervasaari is also a perfect spot to watch unemployed ice breakers floating on opposite shore at Katajanokka. For rose entuastichs Tervasaari offers few rare spices of their favorite flowers.
This cape on Herttoniemi has something why we call this blog as Hidden Helsinki. Kivinokka is truly hidden escape for citizens. There you can see that there is many layers in Helsinki. The one that tourist see in every brochure and then much more interesting layer where you see places such as Kivinokka.
Kivinokka has few hundred tiny summer cottages under shade of trees. Smallest are really the size for hobbits but still there is loads of people spending their whole summer holiday. There is descent beach and smaller coves as well for sun worshipers.