Old Porvoo. This pictoresque old town about half an hour from Helsinki is definitely worth a trip. Small alleys criss-cross the town that is perched on a small hill overlookign river Porvoo. The town was founded in 1346 and is one of six medieval town in Finland.
Porvoo old town is one of the Unesco World Heritage sites. It's still fully habited and cared for by the owners of the building.
