Venice is easy to do pre-cruise. Doug and I adored it. Very romantic.
Barcelona is a small city, easily doable in a short period of time. The city doesn't wrap its arms around you, but the Gaudi architecture is worth the trip alone.
Rome is a must see. So much history. Then you could also do Pompeii or add on Tuscany.
Have not been to Monte Carlo.
If you love to travel and haven't been to any of these cities, you just cannot do wrong with any of these choices.
Just pick a spot and enjoy
