The list is long, but here are some that should definitely be on your list: the Acropolis in Athens, the Coliseum in Rome, the Hermitage in St. Petersburg amongst many other sites!
GRAB A BITE
Pizzasin Italy, borscht in Russia, salmon in Norway, wine in France, cheese in Amsterdam and paella in Barcelona.
WHAT TO PACK
If you are going on a cruise in Europe, it will probably be in the months between May and October. Spring is just about giving way in summer in May - the weather is still bracing and so will need to carry some light weight jacket and clothing, and as the months go on the sun gets hotter so southern Europe and the Mediterranean can get a bit warm - cool cotton clothing will do now, but evenings can see temperatures drop. Walking shoes are a must as there is plenty of walking to be done here.
The Euro is the currency of the European Union. In Russia it is the ruble, in Turkey the Turkish Lira, Norway it is the Krone, and the Kuna in Croatia.