Which places to visit in or near Rome and Venice for 4 Day trip?

My goodness, you could just spend 4 days in Rome and not see everything. I have been there twice and just feel as if I am starting to understand the city. Between Rome and Venice you have several good stops. I wish I knew if you had a car or were using the public transportation system ( watch out for pick pockets in Rome). Between Rome and Venice you have Pisa and Florence as you travel south out of Rome. If you hit Rome, Ravenna, Assisi, Pisa, Florence, and Venice in those 4 days you will have done something. Just outside of Rome is a sight that is worth trying to get to that is the ancient city of Ostis Antica. This is Italy's best preserved ancient settlement after Pompeii and it is only miles from Rome. You can get there using the train. It was an important seaport and had a population of 500,000 by the second century. Assisi is the resting place of St. Francis and is a lovely hill top town. It is on three levels and the streets are very narrow and very ancient. Worth an afternoon stop. I found the people friendly and the town interesting Lots of walking here because cars are not allowed into the town. Ravenna has one of the oldest Christan churches in Italy and is a peaceful place. Good food across the road from the church and would make a good lunch stop. Pisa, of course, has the leaning tower. As you walk into the tower area from the parking spot you will see a lot of vendors selling all sorts of stuff. Florence is the birth place of the Renaissance and a city worth a stay in. So much to see in Florence. In Florence you have the Galleria DELL'Accademia that holds David, the Dumo,the Uffizi, and the Palazzo Pitti. Florence is also the city to buy leather goods and gold. The street of the gold vendors is worth a trip and you'll want to walk the Ponte Vecchio bridge. Florence requires a lot of walking since the main center of the city is closed to traffic, but you can get a cab in the city center if you need to. Finally, this will get you to Venice. Another city of beauty and wonderful things. Take a boat down the grand canal towards sunset and the evening sun lights up the buildings in colors of pink and orange. I got some wonderful photos of the canal doing that. Lots of walking here as well. Advice for Italy. Take very good walking shoes because the walking is major. There is no accommodation for disabilities. Carry a bag that can not be stolen off of you or pick pocketed. I got a PacSafe bag to carry that meets those requirements. Watch out in train and bus stations. The buses and trains coming into Rome are called the pick pocket express it is so bad. Drink only bottle water and carry a scarf in your bag. Women are required to cover their shoulders and heads in churches. No shorts in churches as well. I totally love Italy and would go back in a second for my 3rd trip, but you need to be smart.