Zion is the city of the great King. The prior Psalm (47) proclaims that the Lord God is King. Zion is spoken of often in the Bible and especially in the Psalms.
I have often heard someone say that Zion represents the church. The invisible church from Abraham to the present day; however, I have a few problems with that interpretation.
Firstly, Zion was a real place, another name for Jerusalem especially in the prophetic books or more specifically a mountain in Jerusalem. (OT, Strongs) In the days of the Old Testament, if you wanted to come to God, one had to come to Jerusalem and worship him at the temple. The temple is no more, it was destroyed by the Romans in AD 70.
Secondly, Zion is the city of the great King and God is King of all the earth. (Ps 47:7) After his resurrection, Jesus said to his disciples: “All authority has been given to Me in heaven and on earth.” (Mt 28:18) Jesus is no longer on the earth, he has been taken up from us into heaven, (Acts 1:11) and he sat down at the right hand of the Majesty on high. (Heb 1:3) “Therefore He is able also to save forever those who draw near to God through Him, since He always lives to make intercession for them.” (Heb 7:25)
Zion in the Old Testament is Jerusalem, more specifically the temple mount but Zion in the New Testament is not the church, it is the city of God. One need not go to Jerusalem or the church for salvation but to Christ Jesus because he is in heaven, the true Zion above, he is seated at the right hand of the Majesty on high and he lives to make intercession for us.
Therefore, one need not go to Jerusalem to worship God or make sacrifices and one need not go to the church for salvation. Jesus said, “I am the way, and the truth, and the life; no one comes to the Father but through Me. If you had known Me, you would have known My Father also; from now on you know Him, and have seen Him.” (Jn. 14:6-7) You can go directly to God through repentance and faith in Jesus Christ. The church is not Zion, the city on the holy hill. The church is the fellowship of believers in Jesus Christ.