Maragha observatory

Maragheh observatory (Persian: نپاهشگاه مراغه‎‎), was an institutionalized astronomical observatory which was established in 1259 CE under the patronage of the Ilkhanid Hulagu and the directorship of Nasir al-Din al-Tusi, a Persian scientist and astronomer. Located in the heights west of Maragheh, which is today situated in the East Azerbaijan Province of Iran, it was once considered one of the most prestigious observatories in the world.

It was financed by waqf revenues, which allowed it to continue to operate even after the death of its founder and was active for more than 50 years. The observatory served as a model for later observatories including the 15th-century Ulugh Beg Observatory in Samarkand, the 16th-century Taqi al-Din observatory in Istanbul, and the 18th-century Jai Singh observatory in Jaipur.

Considerable parts of the groundwork are preserved in the ruins. In a 340 to 135 m² citadel-like area stood a four-story circular stone building of 28 m diameter. The mural quadrant to observe the positions of the stars and planets was aligned with the meridian. This meridian served as Prime meridian for the tables in the Zij-i Ilkhani, as we nowadays apply the meridian which passes the Royal Greenwich Observatory.

...
Wikipedia