- Gerrha may also refer to Ancient Egyptian city and former bishopric Gera (Egypt)
Prior to Gerrha, the area belonged to the Dilmun civilization, which was conquered by the Assyrian Empire in 709 BC. Gerrha was the center of an Arab kingdom from approximately 650 BC to circa 300 AD. The kingdom was under threat of attack by Antiochus III the Great in 205–204 BC, but his forces renounced hostilities once they received a tribute of 500 silver talents from the inhabitants.
Describing the city
Strabo described the city as having "fancy tools made out of gold and silver, such as the family gold, right [Qawa'im] triangles, and their drinking glass, let alone their large homes which have their doors, walls, roofs filled with colors, gold, silver, and holy stones" 
Location and etymology
To the Ancient Greeks, eastern Arabia (the present-day al-Hasa province) was known as Gerrha after its capital city. Gerrha was a Greek alteration of the Arabic Hajar (present-day Hofuf), the name of the largest city of ancient Bahrayn (Bahrayn was also known as Hagar or Gerrha in Hellenistic times). Other English spellings are Hajar Hufuf, Hajar Hasa' Hajarah. Hagar (Gerrha) is not to be confused with the west Arabian Al-Hijr (al-Hijrah), the present-day Mada'in Saleh or al-Ula near the Red Sea. Al-Hamdani says the etymology of Hajar means ‘large village’ in the Himyaritic language (derived from Hakar).
The city of Gerrha was taken by the Qarmatians at the end of the ninth century. It was 2 miles (3.2 km) from the Persian Gulf near present-day Hofuf. The researcher Abdulkhaliq Al Janbi argued in his book that Gerrha was most likely the ancient city of Hajar, located in modern-day Al-Ahsa, Saudi Arabia. Al-Janbi's theory is the most widely accepted one by modern scholars, although there are some difficulties with this argument, given that Al-Ahsa is 60 km inland and thus less likely to be the starting point for a trader's route, making a location within the archipelago of islands comprising the modern Kingdom of Bahrain, particularly the main island of Bahrain itself, another possibility.
Origins of the inhabitants of Gerrha
As Gerrha is located in the Arabian Peninsula, there's no doubt that the city's inhabitants were Arab. Strabo described the inhabitants as "Chaldean migrants from Babylon", who build their houses of salt and repaired them by the application of salt water; though in another passage he describes them as Arabs, saying, "Because of their trade, the Gerrhans became the richest of the Arabs". Other sources agree that the inhabitants were indeed Arab. Also, petroglyphs were found in Greece and were found to have been sent by a man from Gerrha called Taym Al Lat, which is undoubtedly an Arab name.
- Chisholm, Hugh, ed. (1911). "Gerrha". Encyclopædia Britannica. 11 (11th ed.). Cambridge University Press.
- Hans Volkmann. "Antiochus III the Great". Encyclopaedia Britannica. Retrieved 1 August 2018.
- Strabo, Geography, i6. 4. 19-20
- Marx, edited by Angelika Neuwirth, Nicolai Sinai, Michael (2010). The Qur'an in context: Historical and literary investigations into the Qur'anic milieu. Leiden: Brill. p. 227. ISBN 9789047430322. Archived from the original on 2010.
- Hamdani, al-Hasan. Geography of the Arabian Peninsula. p. 236.
- Smart (1997). New Arabian Studies Vol 4. Exeter. p. 213. ISBN 0859895521.
Hagar is name of Bahrain division and its capital
- Tareekh al-Bahrain: Shaikh Tahir al-Qassimi, pages 53-65
- Abdulkhaliq Al-Janbi. Gerrha, The Ancient City of International Trade جره مدينة التجارة العالمية القديمة.
- Larsen, Curtis (1983). Life and Land Use on the Bahrain Islands: The Geoarcheology of an Ancient Society. University of Chicago Press. ISBN 0-226-46906-9.
- Arabia and the Arabs: From the Bronze Age to the coming of Islam (2002), Robert G. Hoyland, p. 25.
- Bibby, Geoffrey (1970). Looking for Dilmun. Collins, London. ISBN 0-00-211475-5.
- Potts, D. T. (1990). The Arabian Gulf in Antiquity Volume II: From Alexander the Great to the Coming of
Islam. Oxford, Clarendon Press.