Even though I have travelled quite a lot, I'm not a travel-guide. One thing I have learned: to see things that interest you. Others may think a place is the best place they have ever been, but you don't find it interesting - that's because people are different. So follow your interests.
I have made 4 interrail-trips in Europe when Interrail was "in" in the 1980's and here I have seen many cities. Since then I have discovered that I often prefer trips to places with great nature instead of trips to cities. The reason might be that the nature is quite unique whereas cities tend to like the same, especially as chains af Seven-Eleven and McDonalds is found everywhere.
This just to illustrate my preferences - yours may be the same or the opposite.