An ancient citadel stands in the southeast corner of the old walled city of Harran. This citadel dates back to 2000 BCE when the Sabians built a temple to the god Sin. In 642 CE Harran was overrun by the Muslim armies, and later, Caliph Marwan II made Harran his capital from 744 - 750 until it was conquered by the Abbasids in 750 CE. Marwan II built a mosque in the center of the city and a royal palace on the site of the temThe citadel was rebuilt several times, once after 990 CE when Harran became the capital city of the Numayrids, a local northern Syria dynasty ruled by Waththab bin Sabiq al-Numayri. An inscription on the gateway dates it construction to 1059 CE. Nur al Din rebuilt the citadel in 1149. In 1259 the city was overrun by the Mongols and one of the two towers was destroyed. In 1271 the Mongols moved most of the population away and the town was deserted and mostly destroyed. The current citadel structure dates back to the 14th century.

The structure that is of interest to us is the mosque and university built in the centre of the city. During the late 8th and 9th centuries Harran University was a centre for translating works of astronomy, philosophy, natural sciences, and medicine from Greek to Syriac by Assyrians, and thence to Arabic, bringing the knowledge of the classical world to the emerging Arabic-speaking civilization in the south. Baghdad came to this work later than Harran. Many important scholars of natural science, astronomy, and medicine originate from Harran; they were non-Arab and non-Islamic ethnic Assyrians, including possibly the alchemist Jabir ibn Hayyan. Other philosophers and scientists include Al-Battanai who calculated the distance from the Earth to the Moon and Thabit ibn Qurrah, who translated Greek classics and scientific works into Arabic, and wrote on mathematics and astronomy.

The Sabians revered Hermes Trismegistus as their prophet and the Corpus Hermeticum as their holy book. Hermes Trismegistus was believed to be an ancient great Egyptian sage, who as the founder of writing and the author of many books on science, medicine, theology, ethics, astrology, alchemy and magic. In the Hermeticum scriptures his teachings appear in the form of mystic visions. Hermeticum portrays Hermes Trismegistusas a divinely inspired teacher, but others have portrayed him as the Greek god Hermes, and the Egyptian god Thoth or Tehuti. Some have equated him with Enoch in the Bible, and Idris in the Koran. Through the Hermeticum’s monotheistic teachings, the Harranians where able to claim themselves as one of the “People of the book” though the term Sabian might have referred more to the Mandaeans of Iraq, who are Gnostics and known as followers of John the Baptist.

Neither the university building nor the citadel seem to have any qibla direction. The University and mosque in the centre of the city seem to point somewhere between Petra and Meccaple of Sin.