I live in Spain, so I have visited quite a few cities. I would not recommend all of them in one trip! Some of them could be a trip on their own!
I have been fortunate enough to find cheap flights to some other countries. I only spent a few days in each of them and am itching to go back!
I imagine in this section, I will only add Morocco since it is not Europe. However, that should not make it irrelevant. This was a beautiful and life-changing trip!