well, i book travel itineraries for a living,
can you tell me these things please
1. when do you want to travel; when is your travel date, how many days for, how much leeway, what departure airport. i take it you are a US citizen so you have the standard 90 days stamp-on-arrival for all the countries in the greater european area.
2. are you on a strict budget? for both flights and holiday. And how long do you have to stay here?
The time on the ground is important because if you have your 8/9hour flight from JFK or Logan BOS and maybe connecting flight there plus car ride, security, etc and then the same again backwards in a few days, and you try to pack all that plus all the activities in a week or so, you will be tired, man, the "holiday" will exhaust you. The goal of a holiday is that you come back better, not worse.
3. and this is the most difficult to answer ..
What kind of EXPERIENCE do you want and/or expect to have. Do you come to europe to feel like you've stepped into an antique world? See statues and buildings that make you feel like you live in the middle ages? Or are you just looking to have an informed viewing of arts? such as museums, and well again, statues and buildings, but more in a "technical" way that just "let the beauty sweep me off my feet".
Are you looking to stay on a chair and get cocktails handed to you? Do you want to go explore old taverns and order weird foods in a strange language? Do you want to feel the hustle&bustle of a crowded market, do you want shining hotel lobbies, do you want to buy fancy new clothes or old cloth? Ethnic or modern?
Are you looking for a life-changing experience, or for a conversation piece?
Remember that, for how modern and reasonably well organized we are in Europe, you are still travelling to a foreign country. While things will probably go smooth, they can still go wrong. A solid travel insurance policy (should be failry cheap, $100 or less, although it may be higher if you have preexiting conditions) is gonna be needed as well.