Helsinki
Parks
Lake Toolonlahti and Hesperianpuisto Park - Lake Toolonlahti is the perfect spot to kick back and relax for a couple of hours. In the park, there's a playground and tiny sandy beach where toddlers can splash in the water, plus a little waterfalls and stream to play in and rocks to climb on. Look for ducks and their ducklings, paddling around the reeds. At the southern end of the lake, you can rent pedal boats, row boats or kayaks - great fun to boat around the lake, into the reeds, close to the big fountain in the center. Also, it's just a peaceful walk around the lake too.
Linnanmaki Amusement Park and Sea Life Aquarium - The Linnanmaki amusement park has delighted Finnish families for generations. Little kids will enjoy the monorail and little train, or miniature pool where they can paddle around. Older kids will get a gasp out of the roller coasters and water rides, especially the Hurjakuru, where you float on a rushing river past a waterfall. Sea Life Aquarium has tropical fish from coral reefs, a sea horse exhibit, fish swimming in and out of an "underground shipwreck," and a circular tank glowing with silvery schools of fish from the Baltic Sea. (The Aquarium is a good place to duck into during a summer rain shower).
Sibelius Monument and Park - Jean Sibelius is Finland's best loved composer, famous for his symphonies that evoke the Finnish landscape. The Sibelius Monument is like a huge bunch of frozen organ pipes, and in the benches next to the monument, you may find musicians playing.
The surrounding park is delightful - there's a small playground with climbing structures, and lots of trees and paths to simply expend some energy. Or, you can take a walk down along the water or enjoy the small but nice miniature golf course (on Mechelingatan).