Kalev (M414)

The Kalev (M414) is a Soviet-era submarine you can actually step inside at Tallinn's Seaplane Harbour — one of the coolest maritime museums in Europe. The sheer scale of the historic seaplane hangar alone is worth the trip, and with around 200 authentic exhibits including icebreakers and flying boats, this place goes way beyond your typical nautical display. Hop on bus 73 from Vabaduse Väljak and you're there in 15 minutes.