When the Abbasids defeated the Umayyads, they eventually decided on founding a new capital city. Under Al Mansur they built the city of Baghdad, blending knowledge of astrology and urban planning to birth a city of wonder.

A thread on astrology and Baghdad -AAO

Al Mansur settled on Baghdad’s location in proximity to the old Sassanid cities & called upon Indian & Central Asian city-planners to build it round in the Persianate fashion, but in order to build a truly wondrous city he called upon the powers of astrology -AAO

He turn to the Persian Nawbakht and the Jewish astrologer, Mashallah ibn Athari. -AAO

Together they employed ikhtiyārāt, a type of astrology used to elect the most auspicious timing for an event.

Want to know the perfect day to get married, to sign a contract, or even to wage a war, ikhtiyārāt can provide the answer -AAO

Using ikhtiyārāt Nawbakht and Mashallah elected July 31 762 for the founding of Baghdad. The historian and contemporary astrologer, James Holden used the Persian Al Biruni's records to recreate the horoscope.

I’ve attached a contemporary version -AAO

Using the principles of ikhtiyārāt we can see that Nawbakht and Mashallah chose a time where Al Qaws or Sagittarius is rising and in Jupiter, its natural ruler.

This would was chosen to capture the influence of both stars on matters of the mind, philosophy, and justice. -AAO

We can also see, they chose when the Sun would be in Assad/Leo in the 9th House, the house of learning.

Along with the positive aspects all of this would add up to a city “birth” that would ensure a center of learning, wealth, justice, and splendor -AAO

And indeed for hundreds of years, Baghdad was the intellectual and cultural heart of the Islamic world. -AAO

For historians this story provides a unique example for understanding the intellectual Islam that emerges under the Abbasids, one that synthesizes Greek and Persian astrology with advanced Indian mathematics for precise astronomical calculations. -AAO

When Al Mansur built Baghdad, it was a crowning achievement for his Islamic empire, but also evidence of the way in which local and diverse cultures and intellectual traditions were synthesized and incorporated. -AAO