I went straight to Wikipedia for this. Their article David (Michelangelo) 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) 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.