What is the best area to stay in a hotel in Rome and Venice?

Venice is divided in 6 quartiers (sestiere singular, sestieri plural). I suggest Dorsoduro and San Marco (Saint Mark), they're in the centre and from there you can easy visit all the city. Also, they're divided by the Canal Grande and connected by the famous Rialto Bridge. San Marco is probably the best but the most expensive too. Look for good prices on there or for Dorsoduro. In Rome just look for an hotel in centre. There are bus and metro, and really everywhere, every street, every square is full of monuments.. As consequence it could be said that every hotel is in the middle of the monuments to visit >.> :-)