Why does the Book of Mormon mention synagogues?

While its origins are unclear, the synagogue has roots in the biblical period prior to the destruction of Jerusalem by the Babylonians in 587 BC. Some scholars believe that the city gate and its vicinity were the first synagogues, as later synagogues were built to resemble this area. At its most basic meaning in both Hebrew and Greek, the word simply meant a place of gathering or assembly. In light of the above, it is conceivable that any building, structure, or designated location that functioned as a Nephite place of worship could be considered a synagogue.