One of the better services around is the NYC Walk New Yorks Cultural Walking tour guide.
Alfred Pommer is your host and a studied guide.
“The theme of my neighborhood walking tours is to unite us with the past through history, architecture, pictures & stories. We explore Manhattan’s many neighborhoods through its unique landmark skyscrapers, turn of the century mansions, brownstones, clubs, public building & historic districts. Many New York City or national landmarks with historic (Romanesque, Classical, Baroque, Queen Ann, Gothic, Renaissance) or anti-historic (Art Nouveau, Art Deco, Modern, Post Modern) styles of architecture are included. My specialized tours cross neighborhood boundaries and focus on various other themes such as: gargoyles, Jewish history, Irish history, Italian history and outdoor art / sculpture.”
For the creme de la creme this is the way to get intimate with the city.