Big cities with most beautiful scenery in the U.S.

A lot of the big major cities are often pretty dirty or are just complete concrete jungles for the most part (ala NY)
And a lot of the places that are really "green & clean" and have nice natural settings are tiny and don't offer anything that the major cities do

What are the best of both worlds cities here in the U.S.? Major metropolitan area wraped in nice natural scenery>