Take a walk around the Töölönlahti on a sunny day. From Railway station towards Finlandia house. Admire on the route the Sanoma glass palace, the Music House - who visits the place actually - think sadly of the magazines that were torn down and burned from the place. Follow the route close the water to Winter garden and drop in. Walk beside Linnanmäki and wander between the houses and pubs of Kallio back towards Pitkäsilta. Avoid the Helsinginkatu area in the evening unless used to just a tiny bit rougher environment. Walk with a friend with you at Kaisaniemi park but perhaps not in the dark. If the hall of Hakaniemi is open - drop in for a coffee.Follow the tram route back to Railway station.
Place with nature in the middle of the city. You can find many cafes, restaurant, park, swans, wooden villas there and also Finlandia Hall, National Opera, Botanical Garden of Helsinki City. A lot of people go there jogging, or just walking around the bay. We used the walking path by the sea while walking from the train to National opera.
A nice large, wooded park behind the train station this is a nice place for an afternoon stroll. If you are visiting the Olympic stadium then I recommended walking through this park to get here. The large ponds are always full of ducks so good for kids with a loaf of bread.