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 attacked by Antiochus III the Great in 205-204 BC, though it seems to have survived. It is currently unknown exactly when Gerrha fell, but the area was under Sassanid Persian control after 300 AD.
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 Hagar (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 hofuf, hagar hasa' hagara. Hagar (Gerrha) is not to be confused with the west Arabian Al-Hijr (al-Hegra, Hegra), the present-day Madaen Saleh or al-Ula near the Red Sea.
The city of Gerrha was destroyed by the Qarmatians at the end of the ninth century when all 300,000 of its inhabitants were massacred. 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 exiles from Babylon", 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.
- Strabo, Geography, i6. 4. 19-20
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Hagar is name of Bahrain division and its capital
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Hagar is the name of Bahrain and its capital Hagar destroyed by Qarmatians
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