Thanks Warsaw traveller
Krakow has always interested me, not only due to Auschwitz, a big part of history, but also he salt mines, which have heard are amazing.
Im hoping to go more start of September so hopefully the crowds will have died down a bit by then!
Im not sure if ill have time to fit in Warsaw, but if get more time than will try and fit it in....w
You can also hike in the Tatras from Slovakia, don't forget! It's a bit more off the beaten path, so quieter, but really lovely. You'd connect via Poprad to a series of small towns in the mountains themselves. Relatively easy to go south or west from there (or get there from the east if you're coming across from Zurich via Austria!)
Auschwitz takes a full day from Krakow, but you can also do it from Katowice, or stopover in Katowice if you're passing through and want to break up the travel time. I highly recommend Krakow - it's a beautiful city, and I found it a lot less crowded than Prague or more western cities. I'd also recommend the Baltics, if you can. Beautiful beaches, interesting history, people are friendly, relatively cheap...
Czech is beautiful, but try Brno, and some of the nature areas if you're heading that way. The moravian karst region, and the pavicka brana in the north near Decin.
I loved Iceland! - side note
Feel free to check out my maps as I've done a lot of traveling in some of these areas, and would be more than happy to help if you have more specific questions.