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Bus

Buses travel between Porvoo bus station and Helsinki's Kamppi every 30 minutes or so (€9 to €15, one hour). There are also frequent buses to/from towns further east.

Boat

The noble old steamship JL Runeberg cruises from Helsinki's kauppatori to Porvoo's passenger harbour in summer (one way/return €27/39) and makes an excellent day trip, with various lunch options available. The trip takes 3½ hours each way, so you may prefer to return by bus.