having been to New york many times its difficult to decide. agree with all the answers, and it was very moving to see ground zero and all the tributes when I visited in 2002, However St Patrick's Cathedral on 5th Ave is very peaceful and a warm welcome, lovely masses, from the roof hang cardianals hat I am sure many miss these, I asked a guide and he said they no longer hang up the hats when a cardinal dies, you would never believe once inside you are on the busy 5th Ave as calm inside, as anyone who knows NYC will be aware of the constant noise of traffic on 5th Ave , Also a must has to be Grand Central station.