1. Tallinn, Estonia (by ferry)
The single most popular day trip from Helsinki. Tallinn's fairy-tale medieval Old Town — a UNESCO World Heritage site of cobbled lanes, guild houses and city walls — sits just across the Gulf of Finland. Fast ferries make the crossing in about two hours, with up to 9.5 hours to explore before you sail back for dinner. Best for: history, architecture, a "two countries in one trip" story.
- Return day-trip ferry ticket
- ~2 hours each way · several daily sailings
- Up to 9.5 hours in Tallinn's Old Town
- Remarkable value for a second country