Maragheh observatory (Persian: ? ) was an astronomical observatory 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 "the most advanced scientific institution in the Eurasian 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. It served as a model for later observatories including the 15th-century Ulugh Beg Observatory in Samarkand, the 16th-century Taqi al-Din observatory in Constantinople, and the 18th-century Jai Singh observatory in Jaipur.
There were multiple buildings constructed at the observatory site including a main building and five circular buildings containing observational instruments for astronomical research. Living quarters were also present on the site as well as a building for metalworking. There was also a 330 m2 building that was used as the library. It is said that at one time the library held over 400,000 volumes of literature related to astronomy and astrology.
The main building is circular with a diameter of 22 m. The entrance was 1.5 m wide and opened to a hallway that was 3.1 m wide that marked the meridian line. There were six rooms on either side of the hallway. These structures were made of mainly clay, brick, and mud. The final structure at the observatory was a tower. In a 340 × 135 m citadel-like area stood a four-story circular stone building with a diameter of 28 m.
The mural quadrant to observe the positions of the stars and planets was aligned with the meridian. This meridian served as the prime meridian for the tables in the Zij-i Ilkhani. In total the observatory spans an area of 150 m by 350 m. Today, considerable parts of the groundwork from these structures are preserved in the ruins.
Due to recent discoveries and unearthing of the foundation of the observatory they have found that its construction has helped set the basis for other known observatories. Ulugh-Bey used its extravagant size and such practical use that he established an observatory at Samarqand in the 14th century with similar scaling. The Ulugh- Bey observatory was in turn used as the blue print for more early day European observatories as well such as Kepler. 
The construction of the observatory began in 1259. Construction lasted a total of three years. This is according to multiple books including Jam-e-ttavarikhe rashidi (Persian ), saf-e-elhofreh (Persian: ), and favat-o-lvafiyyat (Persian ?)  The observatory came to be because of Nasir al-Din al-Tusi, a Persian mathematician, astronomer and philosopher. Al-Tusi developed many astronomical theories, but failed to carry them to completion due to a lack of a workspace and resources. When the Mongols started to overtake their land, al-Tusi plead to Hulagu. He stated that with the necessary equipment, he could tell the future. This played into Hulagu's superstitions and was permitted to play this dream into reality. He acted as an advisor to Hulagu, a grandchild of Genghis Khan. Tusi complained to Hulagu that his astronomical tables had to be adapted to the latitude and longitude of Hulagu's new capital. Hulagu gave Tusi permission to build a new observatory in the location of his choosing, and Tusi chose Maragha, Iran, where he became the director of the observatory. Men of mathematics, science, and astronomy came to the Maragheh Observatory from across the Islamic world and further. According to historical texts recovered from the observatory, the site had a reputation so widespread it had reached as far as China as students had traveled to study mathematics, physics, and astronomy. Other scholars in attendance included Bar-Hebraeus, who late in his life took residence close to the observatory in order to use the library for his studies. He has left a description of the observatory.
A number of other prominent astronomers worked with Tusi at the observatory, such as Muhyi al-Din al-Maghribi, Mu'ayyid al-Din al-'Urdi, from Damascus, Qutb al-Din al-Shirazi, and Hulagu's Chinese astronomer Fao Munji, whose Chinese astronomical experience brought improvements to the Ptolemaic system used by Tusi.
After 12 years of intense work by Tusi and other scientists, including Mu'yed al-Din al-Arad-Najmedin Cathy, Najmd al-Din Qazvini, Allame Qutbuddin Shirazi, and Fakhruddin Maraghi, the tables were compiled in the Zij-i Ilkhani. The tables were published during the reign of Abaqa Khan, Hulagu's son, and were named after the patron of the observatory.
The downturn of the Maragheh Observatory began in the 13th century. After the death of Tusi in 1274 his son took over as director. However, with the death of Hulagu in 1265 and his son Abaqa in 1282, the observatory no longer had patrons to fund the research being conducted. The observatory became inactive by the beginning of the 14th century. Over time the site turned to ruins as a result of frequent earthquakes and a lack of funding by the state to preserve the site. Shah Abbas the Great arranged for repair; however, this was not commenced due to the king's early death.
During the Mongol invasions and conquests in this region, the contents of the observatory's library were stolen.
A celestial globe from the observatory made around 1279 is now preserved in Dresden, Germany. It is a rare example of decorative art from Iran of the 13th century, designed by al-Urdi and made of bronze inlaid with silver and gold.
After 1978, Tabriz University, which is located near the observatory, was placed in charge of its preservation. Today the site is home to occasional star parties and, though there are no official tours offered, the public is still welcome to come and see the remains of the observatory.
The observatory is currently covered with a brass dome and is situated two miles west of Maragheh. To save the installation from further destruction, the Cultural Heritage Organization of Iran built a dome-framed shelter and it plans to hold an exhibit of astronomical devices used at Maragheh Observatory.
Hulagu Khan was a Mongol ruler and the grandson of Genghis Khan. As the Mongols expanded their territory Hulagu was put it charge of conquering Mesopotamia, Persia, Egypt, Syria, and the Abbasid Caliphate. From 1253 to 1256, Hulagu and his army were fighting to take control of the region of Iran known as Alamut. It was in 1256 that Hulagu took down the Castle of Alamut. Here he met al-Tusi. Many of the scholars of the region had fled to the mountains for sanctuaries to continue their studies as Tusi had in this castle. However, there is dispute over whether or not Tusi was there against his will, or even somehow helped the Mongols get in and attack.
Tusi was respected by Hulagu for his scholarship in science and decided to make him an advisor. Hulagu and his men, along with Tusi, then went to Baghdad where the city was laid to waste. Hulagu later made Tusi a wazir, or a high ranking advisor or official. He also placed him in charge of waqfs, or religious endowments. Given his trust in Tusi and his respect for the sciences and astronomy, it is not surprising that Hulagu supplied the funding for the Maragheh Observatory when Tusi complained of needing new astronomy tables. He even made Maragheh the capital of his empire.
Nasir Al-Din al-Tusi and his team worked at the Maragheh observatory in the 13th century.  He was born in Tus in the year 1201 A.D. Nasir Al-Din al-Tusi's most notable work was the creation of the Tusi-couple, a geometry based system that solved some of the fundamental issues with the Ptolemaic system's description of planetary motion. He disagreed with the fact that Ptolemy stuck with the overall agreed on idea at the time in the astrology world that the earth was the center of the universe. He also was not a fan with the form that Ptolemy decided to measure the motion of planets such as Venus because of his flawed artificial machinery. This is what lead him to the Tusi-couple. The Tusi-couple uses two different sized circles with the smaller of the two placed with its center tangent to the larger circle. When a point is placed on the smaller sphere and both are set into motion, both rotating at different speeds with the smaller circle's center rotating with the larger circle, the point looks as if it was oscillating about a line. Some other notable works Tusi conducted were commentaries and revisions of Euclid's Elements and Ptolemy's Almagest as well as the astronomical handbook titled Z?j-i ?lkh?n? detailing the movement of the planets, of which he was the lead author. He also helped with the accuracy of astronomy readings with his use of mathematics. Along with it he was able to discover may new stars and help composed and organize new star catalogues with this information. Overall, precision seemed to be a major focus due to the fact that they were able to use trigonometry and calculus when doing his research. Under Nasir Al-Din al-Tusi, there was an expansion of instruments used in the observatory. It is said that under his direction the art of creating instruments reached its peak. The instruments were formed in such a shape, that they lead the competition with their European competitors. 
Muhyi al-D?n al-Maghrib? was an astronomer who worked with Tusi at the observatory. Here he made his contributions the furtherment of knowledge of Astronomy. Here at the observatory, his main goal was to determine the new order of parameters for the Ptolemaic lunar model which was explained in his in his Talkh al-majis, "Compendium of the Almagest." This process was long and strenuous, taking him over eleven years to just collect the starting data. The three Lunar eclipses he used were from March 7, 1263, April 7, 1270, and January24, 1274. He used the collected data for these eclipses to measure the lunar epicycle radius and means of motion. He then used a observation that was recorded on April 20, 1264 to determine the lunar eccentricity. He then complied the information for the new parameters and came up with his model. He tested the model using an observation from April 20, 1264 and another from March 15, 1262 to determine the lunar parallax. He has come to be known as the only Islamic astronomer that left some sort of explanation of how he got to the lunar parameters and data that he fond through his observations to be able to reach his final results. It showed his determination through all the obstacles. 
Shams al-D?n Mu?ammad al-W?bkanaw was born in 1254 A.D. and died in 1320 A.D. Shams al-D?n Mu?ammad al-W?bkanaw? adopted all of Maghribi's parameter values in his Zij but had some minor changes that he wanted to make. He decreased the original parameter value for the mean longitude of the moon of epoch by 0;13,11°. It is claimed that the results given in the astronomical table from his adjustment goes along with true modern tables. The accuracy to true modern tables may be due to his correction in measurements and that his process included analyzing the times of lunar eclipses and new moons during a time frame from 1270-1320 and comparing them. 
Qutb al-Din al-Shirazi was a 13th century Persian Astronomer, mathematician, physician, physicist and scienctist. He was born in 1236AD and died in 1311AD. He was from Shiraz, Iran. While at the observatory he worked with his master Nasir al-Din Tusi and wrote critques of the "Almagest" of Ptolemy. He also continued the studies of Alhazen. He gave the first correct explanation to the formation of rainbows which was later further explained by one of his students Kam?l al-D?n al-F?ris?. Qutb al-Din al-Shirazi produced two prominent works on astronomy while working at the observatory. The first work was the "The Limit of Accomplishment concerning Knowledge of the Heavens" which was completed in 1281. The second work was "The Royal Present" which he completed in 1284. Both works presented his ideas and models for planetary motion. His goal of his works was to improve Ptolemy's principles. In his first work "The Limit of Accomplishment concerning Knowledge of the Heavens" he discussed the possibility of heliocentrism. Outside of the observatory he wrote extensively on medicine, mathematics, and traditional Islamic sciences.
Najm al-D?n al-Qazw?n? al-K?tib? was a Persian Islamicate philosopher and logician of the Shafi'I school. He was another student of Nasir al-Din al-Tusi and a major astronomer at the observatory. During his life he was the author of two major works, one on logic "Al-Risala al-Shamsiyya" and the other on metaphysics and natural sciences " HIkmat al-'Ain. His work on logic was commonly used as the first major text on logic in Sunni Madrasahs and could possibly be the most studied book on logic ever. His logic was inspired by the formal Avicennian system of temporal modal logic, but varies from it in several ways. Avicenna considers ten modalities and examines six of them, where al-Katibi examines thirteen.
Mu'ayyid al-Din al-'Urdi was an astronomer and engineer who was asked by Tusi to come to Mar?gha and help design and construct the observatory. He played a key part in the building of the observatory by producing large water wheels to bring water towards the hill where the observatory would be. Al-'Urdi was noted as one of the instrument makers in the observatory and he wrote the treatise 'Ur's Ris?la f? Kayfiyyat al-ard, which is preserved in a manuscript in Paris, and details the instruments in the observatory that were constructed before 1262 AD. Some notable instruments documented in this treatise include the Mural quadrant, an armillary sphere which was used to measure the ecliptic longitude and latitude, a solstitial armilla which was used to determine the obliquity of the ecliptic, and an equinoctial armilla which was used to determine when the sun entered the equatorial plane as well as the path of the sun.
In the history of Islamic astronomy the thirteenth century was the most important. It witnessed the founding of the Maragha Observatory, the most advanced scientific institution in the Eurasian world.