Kraków is Poland's old royal capital: Wawel Castle above the Vistula, the largest medieval market square in Europe, and St. Mary's trumpeter. Kazimierz, the former Jewish quarter, is now one of the liveliest parts of town, a short walk from the Planty ring.
Nearby Wieliczka salt mine is a separate day trip many visitors add. The old town is dense and walkable; nights run late on the square and in Kazimierz. From Gdańsk it is a full day's drive and a different Poland: south, royal, and tourist-busy.