Utrecht is easy to reach by train - just take Thalys to Rotterdam then local train over to Utrecht. Really nice but larger city - lots of nice museums, canal boat trips and famous cathedral and neat town center. Can get direct trains to Schiphol from Utrecht C.S.

Utrecht is the train hub of the Netherlands. Very easy to go anywhere from there. Utrecht - Schiphol is about 30 minutes. (to compare: Amsterdam CS - Schiphol is 20 minutes)

In contrast to most of the country north of the big rivers, Utrecht is a catholic city with much of its medieval past still showing. This is different from most cities in the northern netherlands that were frozen in time shortly after the 17th century, hence the cookie cutter look to them. Utrecht is different. Also a university town, and beautiful churches and museums, as PalenQ already mentioned. The pace is far more relaxed than Amsterdam and the scale more human, especially now that tourism in Amsterdam is exploding.