Great question — answering as the UphillTech team:
It's possible to do both in one day, but I wouldn't recommend it - it's a lot to take in, and makes for a very long day. There's so much to see in Krakow old town, that it's worth spreading them out and spending your down time on a city tour or just walking around trying random foods in old restaurants or seeing the performers in the main square, or just sitting in the parks. What I did can be read on my blog, so I'll include the links: The Wieliczka Mines Auschwitz and Birkenau They are run by Cracow City Tours , and were pretty reasonable. Now, the reason I suggest a tour. For the mines, you'll find that as an individual it's possible to get out there (see Wikitravel for bus numbers and...
Full answer by Mark Mayo: https://travel.stackexchange.com/a/5375 (CC BY-SA 4.0).
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