Hieron (Greek Ἱερόν, Turkish Anadolu Kavağı) was a port, settlement, and fortress on the northern shore of the Asian coast of the Bosphorus. The upper castle of Hieron Castle (Turkish Yoros Kalesi) is located on the summit of a promontory around 800 m from the pier of Anadolu Kavağı. While the upper castle is open to the public, much of the lower fortifications are not accessible since they are in a military zone.

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History

In antiquity, the name Hieron simply referred to its sanctuary (Greek hieron), thus also implying it was famous for being “the Sanctuary.” Various legends report that the Argonauts or Phrixos established a sanctuary (dedicated to the twelve gods or Poseidon) at Hieron. By the 1st century BC, it was the site of a temple dedicated to Zeus Ourios (“of the fair winds”). During this period, its ownership was disputed by Byzantium and Chalkedon. Since Hieron is where the Black Sea first comes into view, it was often considered the starting point of the Black Sea trade route, with Hieron being the point from which all Black Sea navigational charts took their measurements. There was a beacon at Hieron from a very early date, while a lighthouse was built later.

By Late Antiquity, Hieron was the site of the customs station and military base of the Bosphorus (similar to Abydos on the Dardanelles). According to Procopius, after Justinian took office, he set up a customs office in Hieron and Abydos, which excessively collected duties. During Justinian’s reign, the comes (“count”) of the straits of the Black Sea was based in Hieron during a war with Huns of Crimea. The comes at Hieron was later a subordinate of the droungarios (admiral) of the Fleet. The kommerkiarios (fiscal official) at Hieron are documented by seals dating between the 7th and 9th or 10th centuries. Empress Eirene reduced the kommerkia levied at Hieron and Abydos in 801, though these measures were reversed during the reign of Nikephoros I.

Due to its strategic significance, it was often the site of key historical events. John Chrysostom was briefly banished to Hieron in 403. In 764, the Black Sea froze, and wind blew icebergs towards the Black Sea coast and down the Bosphorus, hitting Hieron and the sea walls of Constantinople. Thomas the Slav, during his siege of Constantinople in 821-822, occupied the area to make sure no enemies were at his back and to attempt to gain local support. In 941, a large Rus’ fleet entered the Bosphorus to attack Constantinople. Even though they were thwarted, they continued attacking the region, ravaging the eastern shore of the Bosphorus. The Byzantine fleet came to Hieron and ambushed the Rus on the Bosphorus, destroying much of their fleet with Greek fire.

It is unclear when the current castle was built at Hieron, as there is no record of it being constructed. However, it is generally accepted that it was built by either Manuel I Komnenos (1143-1180) or Michael VII Palaiologos (1261-1282). Once it was finished, it probably housed a large garrison. The Ottomans attacked the castle of Hieron (along with Chele and Astrabeke in western Bithynia) in 1304. Hieron was briefly occupied by the Ottomans in 1306, during which time its residences had to pay tribute. After the Genoese of Pera attacked a Venetian ship in the Aegean in 1328, a Venetian fleet came to Constantinople demanding reparations. When Pera refused to comply, the Venetians blocked the port of Hieron for 15 or 20 days, keeping ships from entering or leaving the Black Sea. The capture of a Byzantine fishing boat at Hieron was the first of a series of incidents that led to a military conflict between the Genoese and Byzantium in 1348. This led to the Genoese gaining control of Hieron, which was then known as Giro. In 1391, the Ottoman sultan Bayezid I captured Hieron and also had Anadolu Hisarı built by the shore of the Bosphorus to the south. Boucicaut, the marshal of France sent by Charles VI to aid the Byzantines in 1399, was unable to capture Hieron. Ruy González de Clavijo, who visited the court of Timur in the early 15th century, refers to Hieron as the “Turkish” castle, which he reports as being inhabited – while the “Greek” castle on the opposite shore of the Bosphorus was in ruin. He also claims that a chain was once pulled across the Bosphorus between the two castles. In 1414, the Genoese once again held Hieron, while the Ottoman captured it by the time of the conquest of Constantinople in 1453. During the reign of Bayezid II (1481-1512), Yoros Castle was repaired, and a mosque and bath were built in the castle. New fortifications were built along the shore by Murad IV in 1624. There was a Turkish quarter within the castle around the beginning of the 19th century, though it was later abandoned that century. The area of the castle was also used for military purposes during the Republic era, though the upper castle was later transferred to Istanbul Metropolitan Municipality, while military lodgings were built in the 1980s.