Russian Czar Alexander I invited representatives of the clergy, classes and traders to the town at the end of hostilities in 1809. Finland then became part of the Russian empire until independence just over a century later.
Saturday's ceremonies were opened in Porvoo Cathedral by Prime Minister Matti Vanhanen, who reminded his audience of landmarks in Finnish history up to the country's accession into the European Union.
For her part, President Tarja Halonen concentrated on current challenges that bind Finland and its neighbours Sweden and Russia closely together. Protection of the Baltic Sea was one such challenge she mentioned.
Numerous other events were held in Porvoo to mark the occasion including street theatre, dancing and concerts.