Visit the island of Soumenllinna

Suomenlinna is a must, also the two cathedrals and the market place on the harbor, although it's quite touristic. If you're into museums, Kiasma.

Be careful on the subway! I was fined 80 Euros for an honest tourist mistake. See my blog for the full story.

Visit the Market Square and the nearby Orthodox Cathedral, and take from the market square the public transport ferry to Suomenlinna. For Shopping, tha the metro to Itäkeskus. If you have more time, take a sightseeing boat for a canal ride, or visit the Nuuksio National park in the neighbour town Espoo, reachable in one hour by local public transport, from Helsinki. Kiasma for modern art, Ateneum for a wider scale of paintings, Design museum for contemporary design. Temppeliaukio Church also for musical presentations; Kaapelitehdas for small museums of different kinds and nearby Ruoholahti as an example of newer housing area.

you have to go to suomenlinna, an island in front of Helsinki (actually a bounch of little islands, linked by bridges). it's a UNESCO world heritage site. faboulos