Trojmiasto covers three cities, each with a distinct character, connected by the SKM commuter rail. Gdansk anchors the southern end with its reconstructed Hanseatic Old Town and the heavy history of the Solidarity movement. Sopot in the middle is the Baltic resort — beaches, pier, and summer nightlife. Gdynia to the north is the youngest and most modernist, with a waterfront packed with museum ships and a well-preserved interwar downtown.
The most efficient approach is to base yourself in one city — Gdansk is the most rewarding for most visitors — and take the train between them. The SKM runs frequently and the journey from one end to the other is around 40 minutes.