The Origin and Location of Synagogues
A Brief History of Jewish Synagogues

Acts 17:10 says that when Paul and Silas arrived in Berea, they went to “the synagogue of the Jews.” What was a synagogue? The word is a Greek term that literally means “a bringing together” (syn together, agō to bring), as a collection of things, or a gathering of persons.
The Jewish synagogue that is found in the New Testament was a Jewish institution[1] that first appeared during the Babylonian captivity. It may have started on the banks of the Tigris and Euphrates rivers by groups of Israelites who, for the first time in their history as a nation, found themselves outside of their land, enslaved by the “impure” Gentiles, with no temple or religions life. There they would gather to weep about the lost glory of Israel (Psalm 137).
Because of these circumstances, faithful Jews began to meet on a regular basis outside of the cities near river or seashores. There they could take purification baths in “living water”[2] and encourage one another by reading the Prophets.
When the Jews returned to Jerusalem under Nehemiah and Ezra, they brought this practice with them. Even after the temple was rebuilt, synagogues functioned in parallel with it, for while there was only one temple in Jerusalem, scattered Jews gathered in synagogues in many places. When the rebuilt temple was destroyed, these meeting places became the only centers of the religious and political lives of Jewish communities. They also became places for teaching and learning.
Through the 2nd century BC, the Jews continued their custom of building synagogues outside the city walls. It was not that the Gentiles shunned them, but the Jews wanted to maintain their purity by gathering away from the cities near rivers (or seashores).
Over time, as the Jews became less religious and more secular, they' began to move their synagogues inside the cities, close to the city center, to elevate their social status and increase their political power. This was especially true in large cities like Thessalonica, Athens and Corinth and is why Paul found the synagogues in these places near the agora.
Endnotes
[1] A.R.S. Kennedy, Hastings Dictionary, 882-884.
[2] “The ‘living,' i.e. ‘flowing’ water of the spring is greatly preferred to the ‘dead’ water of the cistern, and frequently it stands for the vitalizing influences of God’s grace” (John 7:37-38; Jer 2:13; Zech 14:3). W. Ewing, Hastings Dictionary, 966.