Zion signifies the temple in Jerusalem,1 that was the place where the Lord had chosen to dwell amongst his people. Zion and Jerusalem are mentioned together as rebukes to the northern shrines whose false worship Amos so roundly renounces: Bethel, Gilgal (Amos 4:4; Amos 5:5), Beersheba (Amos 5:5; Amos 8:14), Samaria and Dan (Amos 8:14); they are not the centres of revelation and power.2
2 And he said: “The LORD roars from Zion and utters his voice from Jerusalem; the pastures of the shepherds mourn, and the top of Carmel withers.”