The Science of the Cosmos and Great Navigation

The Giralda as an Observatory – Science in the Heights

When the Almohads designed the tower for the Great Mosque of Seville in the 12th century, they were not merely seeking to build the tallest minaret in the Islamic West. Under the direction of architect Ahmad Ben Baso and the influence of scientists like Al-Bitruji (Alpetragius), the Giralda was conceived as a first-class vertical astronomical observatory.

1. Height and Visibility: A Clear Horizon

To study the stars, elevation is essential. Standing at nearly 100 meters in its original structure, the Giralda provided royal astronomers with a privileged platform, free from the city’s visual obstructions and the low mist of the Guadalquivir River.

• Access Ramps: Unlike other towers, the Giralda is climbed via ramps instead of stairs. This allowed astronomers to carry heavy precision instruments (such as large astrolabes and quadrants) to the top and even access the summit on horseback to transport observation materials quickly.

  
  

2. The Seville School of Astronomy

Seville became the epicenter of criticism regarding the Ptolemaic model. Scientists like Ibn Aflah (Geber) worked in the city, and their writings on trigonometry and astronomy influenced the construction of instruments that were likely used at the top of the tower.

• Fixed Instrumentation: It is believed that the upper terrace was used for measuring the altitude of the Sun and stars, essential for correcting calendars and navigation tables.

  
  

3. Symbolism of the Spheres: The Yamur

The original crowning of the Giralda was not a statue (the current Giraldillo), but the Yamur: four golden bronze spheres of decreasing size.

• Astronomical Significance: Beyond their aesthetic and religious value, the spheres represented the structure of the cosmos according to the vision of the time—a universe of concentric spheres reflecting the perfection of the divine order.

  
  

4. The Giralda and Navigation on the Guadalquivir

From the top of the tower, watchmen and scientists looked at more than just the sky. The Giralda functioned as a terrestrial lighthouse, allowing for the coordination of river traffic and the city's defense, merging civil security with cosmic observation.

"The Giralda is a testament to architecture that did not settle for touching the sky, but sought to understand it. Every ramp was designed so that knowledge could ascend as easily as the observer."