On a hill west of the town are the remains of the famous Maragheh observatory called Rasad Khaneh, constructed under the direction the Ilkhanid king, Hülagü Khan for Nasir al-Din al-Tusi. The building, which no doubt served as a citadel as well, enclosed a space of 340 by 135 meters, and the foundations of the walls were 13 to 2 meters in thickness. The observatory was constructed in the thirteenth century and was said to house a staff of at least ten astronomers and a librarian who was in charge of the library which allegedly contained over 40,000 books. This observatory was one of the most prestigious during the medieval times in the Islamic Empire during the golden age of Islamic science. The famous astronomer Ibn al-Shatir did much of his work in this observatory.