Avnik Castle, locally known as Avnik Kalesi, lies atop a mountain next to the village of Güzelhisar, in the province of Erzurum in Turkey.
Avnik Castle is probably of Urartian origin. During Persian or Sassanid rule the castle was known as Ab-Nik. Byzantine sources later called it by the name of Abnikon.
When, in the mid-11th century the Seljuq Sultan Tughril and his brother Ibrahim Inal, passed through the region during their wars with the Byzantines, they were not able to conquer Avnik Castle. In 1071 the castle fell into Saltukid hands and became a border fortress. The Saltukids carried out restorations to the castle, as proven by architectural traces.
In the early 14th century the castle was rebuilt by the Ilkhanid Sultan Oljeitu. Although not much remains of the castle today, it certainly was rather famous in its day. It is even said that Oljeitu's son; Abu Sa'id Bahadur Khan, ascended the throne of the Ilkhanate state, in Avnik Castle in 1316. Later in the 14th century, during the reign of Tamerlane, the castle was repaired.
It is said that in the early 15th century, during Kara Koyunlu (Black Sheep Turkomans) rule, Avnik Castle was used as a refuge by the family of Shah Kubad, the son of the Kara Koyunlu ruler Qara Iskander.
In the second half of the 15th century the castle fell into the hands of the Aq Qoyunlu (White Sheep Turkomans).
Later the castle was also used by the Ottomans.
Avnik Castle was largely destroyed by an earthquake in 1922 and the castle ruins were used as a quarry by the local villagers.
Avnik Castle is not accessible, at least, I was not able to find a safe way to get in. Too bad, I would have liked to see what remains of this castle inside its walls.