Gonio fortress (previously called Apsaros, or Apsaruntos), is a Roman fortification in Adjara, at the mouth of the Chorokhi river. The oldest reference to the fortress is by Pliny the Elder in the Natural History (1st century AD). There is also a reference to the ancient name of the site in Appian’s Mithridatic Wars (2nd century AD). In the 2nd century AD it was a well-fortified Roman city within Colchis. The town was also known for its theatre and hippodrome. It later came under Byzantine influence. The name 'Gonio' is first attested in Michael Panaretos in the 14th century. In addition, there was a short-lived Genoese trade factory at the site.
In 1547 Gonio was taken by the Ottomans, who held it until 1878, when, via the San-Stefano Treaty, Adjara became part of the Russian empire. In the fall of 1647, according to Evliya Çelebi, Gonio was captured by a Cossack navy of 70 chaikas, but quickly recovered by Ghazi Sidi Ahmed, ruler of the Tortum sanjak, with a force of 1,000 Turks and 3,000 'Mingrelians'.
The grave of Saint Matthias, one of the twelve apostles, is believed to be inside the Gonio fortress. However, this is unverifiable as the Georgian government currently prohibits digging near the supposed gravesite. Other archaeological excavations are however taking place on the grounds of the fortress, focusing on Roman layers.
References:Celje Castle was once the largest fortification on Slovenian territory. The first fortified building on the site (a Romanesque palace) was built in the first half of the 13th century by the Counts of Heunburg from Carinthia on the stony outcrop on the western side of the ridge where the castle stands. It had five sides, or four plus the southern side, which was a natural defence. The first written records of the castle date back to between 1125 and 1137; it was probably built by Count Gunter. In the western section of the castle, there was a building with several floors. Remains of the walls of this palatium have survived. In the eastern section, there was an enclosed courtyard with large water reservoirs. The eastern wall, which protects the castle from its most exposed side, was around three metres thicker than the rest of the curtain wall. The wall was topped with a parapet and protected walkway.