Helsinki is a young capital that looks older than it is. For six centuries Finland belonged to Sweden, and Helsinki was a small trading town behind a sea fortress. Then in 1809 Russia took Finland and made it a Grand Duchy, in 1812 the emperor moved its capital here, and a German-born architect, Carl Ludvig Engel, was hired to build a city fit for an emperor. The result is the white Empire-style center around Senate Square, which is why Hollywood used Helsinki to stand in for Moscow and Leningrad during the Cold War. Independence came in 1917, and with it a burst of Finnish architecture, from the granite castles of Art Nouveau to Alvar Aalto.
It's a city of about 700,000 people with the sea on three sides and more than 300 islands offshore. Locals take three things very seriously: coffee (Finns are usually ranked the world's biggest coffee drinkers per person), design and the sauna, which is not a spa treatment here but a weekly ritual, ideally followed by a jump into the sea. Five days give you time for all three, the islands and a day across the water in Tallinn.
This plan starts on a Tuesday. Day one is the harbor, Senate Square and the two cathedrals, day two the Suomenlinna sea fortress and the Design District, day three modern Helsinki from the railway station to the rock church and an evening sauna at Löyly, day four Tallinn by ferry, and day five Seurasaari, Alvar Aalto's house, the Olympic Stadium and Kallio, the old working-class district where the bars are cheapest and a public sauna from 1928 still burns wood. For the bigger picture, see our page on Finland.