I echo Italy but I feel Italy requires a certain independence- like renting a car. If that's a stretch for you, then I would say Paris and London.
I understand what you are saying, but there is plenty you can do in Italy without a car. I've done both. Countryside--a car is needed. But, you can go lots of places without one: Venice, Florence, Rome, and lots of other less well known places. You can also take a bus tour--which, I know, sounds awful to those who are veteran travelers. But, it can be a great way to see the sights with little trouble. Just find a tour that allows you time to roam on your own. For seeing museums, etc, it can save you LOTS of time. I l had driven a couple of times to Italy when I lived in Europe, but I also decided to take a tour to Rome because I didn't want to fool with all the logistical stuff. It was a great way to go. This tour did allow a lot of time on your own.
For first time travelers, I highly recommend a bus tour.