I went straight to Wikipedia for this.  Their article [David (Michelangelo)][1] states:

> David is a masterpiece of Renaissance sculpture created between 1501
> and 1504, by the Italian artist Michelangelo. It is a 5.17-metre (17.0
> ft)[1] marble statue of a standing male nude. The statue represents
> the Biblical hero David, a favoured subject in the art of Florence.
> Originally commissioned as one of a series of statues of prophets to
> be **positioned along the roofline of the east end of Florence
> Cathedral**, the statue was instead placed in a public square, outside
> the Palazzo della Signoria, the seat of civic government in Florence,
> where it was unveiled on 8 September 1504.
> 
> Because of the nature of the hero that it represented, it soon came to
> symbolize the defense of civil liberties embodied in the Florentine
> Republic, an independent city-state threatened on all sides by more
> powerful rival states and by the hegemony of the Medici family. The
> eyes of David, with a warning glare, were turned towards Rome. **The
> statue was moved to the Accademia Gallery in Florence in 1873, and
> later replaced at the original location by a replica.**

So although you could see a replica at the Florence Cathedral, the real deal is currently at the Accademia Gallery, where it has stood since 1873.


  [1]: http://en.wikipedia.org/wiki/David_%28Michelangelo%29