The hook
Poland's old royal capital, one of the few big Polish cities the war left standing, with a vast medieval square, a hilltop castle, and a nearby salt mine hollowed into underground chapels.
01Why it's worth it
Kraków survived the Second World War largely intact, which is why it still has a genuine medieval and Renaissance core when so much of Poland had to be rebuilt from rubble. Its heart is the Rynek, one of the largest medieval market squares in Europe, ringed by townhouses and centred on a long cloth hall, with the Wawel castle and cathedral of the Polish kings on a rise above the river. The old Jewish quarter of Kazimierz, emptied by the Holocaust, is now a district of memory and nightlife both. Just outside town, the Wieliczka salt mine descends into centuries-old galleries where miners carved entire chapels, chandeliers, and altars out of the rock salt. Kraków is also the base for visiting Auschwitz-Birkenau, which asks to be approached as remembrance, not sightseeing.
02How to experience it
Give the old town and Wawel a day, and go underground at Wieliczka for the salt chapels. Spend an evening in Kazimierz. If you visit Auschwitz-Birkenau, go with the seriousness it demands and allow it to be a heavy day rather than one stop among many.
From the locals
Kraków is the one Polish city nobody in these threads argues about. A Canadian living in Toruń ranked the country's cities without hedging — "the best places to visit in order are: Kraków, Toruń, Trójmiasto" — and laid out the city as a hub: "the old town is beautiful, old Jewish Quarter, Auschwitz tour (1 hr away, easy to get a bus arranged through a hostel), salt mines (1 hr away)."
The other recurring note is about who else is there. "That's a student city with plenty of nightlife catering for students in the old town. No fancy tuxedos needed — bring some złoty and a strong liver." Kraków's old town is genuinely beautiful and genuinely loud; both are true at once, and which one you get depends heavily on the street and the hour.