Batumi (Georgian: ბათუმი, formerly known as Batum) is a seaside city on the Black Sea coast and capital of Adjara, an autonomous republic in southwest Georgia. With a population of 190,000 (2013 census), Batumi serves as an important port and a commercial center. It is situated in a subtropical zone, rich in agricultural produce such as citrus fruit and tea. While industries of the city include shipbuilding, food processing, and light manufacturing, most of its economy revolves around tourism. Since 2010, the face of the city has been transformed by the construction of new high-rise landmark buildings and the renovation of the Old Town. Batumi is located on the site of the ancient Greek colony in Colchis called Bathus or Bathys – derived from the Greek phrase bathus limen or bathys limin meaning "deep harbour". Under Hadrian (r. 117–138 AD), it was converted into a fortified Roman port and later deserted for the fortress of Petra founded in the time of Justinian I (r. 527–565). Garrisoned by the Roman-Byzantine forces, it was formally a possession of the kingdom of Lazica until being occupied briefly by the Arabs, who did not hold it; in the 9th century it formed part of the Bagratid monarchy of Tao-Klarjeti and at the close of the 10th century of the unified kingdom of Georgia which succeeded it.
From 1010, it was governed by the eristavi (viceroy) of the king of Georgia. In the late 15th century, after the disintegration of the Georgian kingdom, Batumi passed to the princes (mtavari) of Guria, a western Georgian principality under the sovereignty of the kings of Imereti.
A curious incident occurred in 1444 when a Burgundian flotilla, after a failed crusade against the Ottoman Empire, penetrated the Black Sea and engaged in piracy along its eastern coastline until the Burgundians under the knightGeoffroy de Thoisy were ambushed during their landing raid at the port of Vaty, as Europeans then knew Batumi. De Thoisy was taken captive and released through the mediation of the emperor John IV of Trebizond.
In the 15th century in the reign of the prince Kakhaber Gurieli, the Ottoman Turks conquered the town and its district but did not hold them. They returned to it in force a century later and inflicted a decisive defeat on the Georgian armies at Sokhoista. Batumi was recaptured by the Georgians several times, first in 1564 by prince Rostom Gurieli, who lost it soon afterwards, and again in 1609 by Mamia Gurieli. In 1723 Batumi again became part of the Ottoman Empire. With the Turkish conquest, the Islamisation of the hitherto Christian region began, but terminated and to a great degree reversed, after the area was re-annexed to Russian Imperial Georgia in the mid-19th century.