The Cordoba Cathedral's bell tower has undergone major changes since Abd Al-Rahaman III entrusted the architect Said Ibu Ayub to built the Great Mosque's minaret in 957.
The minaret underwent its first major work in 1593, by the architect Hernan Ruiz, following storm damaged in 1589. His grandson, Hernan Ruiz III, reenforced the tower's foundations. In 1618 the minaret would totally disappear, propped up and encased in masonry 5 feet thick.
The third level of the tower holds 12 bells, and the fourth holds 2. The oldest was forged in at the beginning of the 16th century and rings the quarter hours.
The Cathedral's bell tower underwent major repair work after the 1755 Lisbon earthquake severely damaged it, and this is the tower we see today, restored and cleaned in the 1990s.
Photo albums of Mezquita
Sources: [Orti Belmonte, p. 219-27, Goodwin p.54]