Which city in Italy is the best for a short break ?

Pisa is a well-known place because of the Leaning Tower, but once you have seen it, there is nothing really much there. Of the places you've mentioned, Venice is the most beautiful and a different kind of place with its unique waterways and water transport systems. It is not necessary to know Italian to find your way through the place...I am not an Italian and had been there last summer. Italy is quite tourist friendly, so you may not have much difficulty. The late evenings and nights look lovely with the lights reflecting in the water....and the sight of the gondolas...it's all actually very romantic - so that would be the best place for a short break.