The Giralda is a former minaret that was converted to a bell tower for the Cathedral of Seville in Seville. The tower is 104.1 m in height and it was one of the most important symbols in the medieval city.
The tower was begun under the architect Ahmad Ben Baso in 1184. After Ben Baso's death, other architects continued work on the tower. The mathematician and astronomer Jabir Ibn Aflah (or Geber) is also often credited with the tower's design. The tower was completed March 10, 1198 with the installation of copper spheres on the tower's top. The Almohads built similar towers in what are now Spain and Morocco during this period. The tower of the Koutoubia Mosque in Marrakesh served as a model for the Giralda and its sister, the Hassan Tower in Rabat.


Bells on the top.
The tower's first two-thirds is a former minaret from the Almohad period of Seville, the upper third Spanish Renaissance architecture. After Seville was taken by the Christians (1248) in the Reconquista, the city's mosque was converted to a church. This structure was badly damaged in a 1356 earthquake, and by 1401 the city began building the current cathedral, one of the largest churches in the world and an outstanding example of the Gothic and Baroque architectural styles. The tower survived the earthquake, but the copper spheres that originally topped the tower fell during a 1365 earthquake, and the spheres were replaced with a cross and bell. The new cathedral incorporated the tower as a bell tower and eventually built it higher during the Renaissance under architect HernĂ¡n Ruiz the Younger, who was commissioned to work on the tower in 1568. This newer section of the tower contains a large inscription of Seville's motto, NO8DO, meaning "[Seville] has not abandoned me." Alfonso X of Castile gave the motto to the city when it continued to support his rule during an insurrection. Covering the top of the tower is the "Lily section" which surrounds the enclosure with the bell. The statue stands 4 m (13 feet) in height – 7 m (23 ft) with the pedestal – and sat on top of the tower from its installation in 1568 until 1997, when it was replaced with a copy.[Source]