interested in science, Hulagu believed him and appointed Nasir al-Din al-Tusi as the scientific advisor of the Mongols. Hulagu allowed Nasir al-Din al-Tusi to build an observatory, and Nasir al-Din al-Tusi chose Maragha, Iran. In 1259, the Maragheh observatory began construction, which took a total of three years to complete. Hulagu also put Nasir al-Din al-Tusi in charge of waqfs which were religious endowments. As director of the observatory, Nasir al-Din al-Tusi and his team were able to make fascinating discoveries in astronomy, physics, and mathematics. Nasir al-Din al-Tusi was the director of the Maragheh observatory, and made many new discoveries while he was there. Such discoveries include the Tusi-couple, a system based on geometry that includes a smaller circle within a larger circle that is twice the diameter of the smaller circle. The rotations of the smaller circle allow a specific point on the circumference to oscillate back and forth in linear motion. The Tusi-couple solved many issues with Ptolemaic's systems over planetary motion. Also, he helped astronomy become more accurate by discovering brand new stars as well as composing a star catalogue with detailed information about each star. Another notable work from Nasir al-Din al-Tusi was an astronomical book that contained detailed notes and observations about the movement of planets. Under Nasir al-Din al-Tusi, scholars from across the Islamic world came to the Maragheh observatory in order to further their studies in math, science, and astronomy. Furthermore, many new instruments were introduced to the observatory, which made him and his team's work a competitor to that of Europe. The Maragheh observatory eventually had its downfall in the 13th century. The Mongol leader, Hulagu, died in 1265, and Nasir al-Din al-Tusi died in 1274. Nasir al-Din al-Tusi's son became the director of the observatory after his father's death, however, there weren't enough scholars at the observatory to fund the research that was being conducted. Therefore, the Maragheh observatory became inactive at the beginning of the 14th century. Over time, the observatory began to crumble due to consistent earthquakes and the lack of preservation of the observatory. Furthermore, the contents of the observatory were stolen during Mongol raids which wiped out important documents and books that were contained within the libraries of the observatory. Universities in Maragheh University of Maragheh Payam-e Noor University of Maragheh Azad University of Maragheh Famous natives For a complete list see: :Category:People from Maragheh Sister