I cannot choose just one.
When I'm in London I feel like I belong there.
Florence is the most romantic, wonderful, uplifting city in the world to me. Plus I love the Tuscan hillsides and hill towns... the wine doesn't suck.
Turkey is just awesome: Istanbul is the most interesting city to me. Kushadasi is peaceful, the ruins at Ephesus, my favorite, and Antalya is a great resort (though not my favorite).
I spent many of my childhood summers near Lahina in Maui, and that holds a special place in my heart.
Paris, in many ways, is my favorite big city.