The Holy City

The Holy City (the New Jerusalem) is Christianity, made up of the twelve tribes of Israel and the twelve apostles of the Lamb. The twelve tribes of Israel constitute the Old Testament, and the twelve apostles of the Lamb constitute the New Testament. This means that the Holy City is the Holy Bible, made up of the Old Testament and the New Testament.

The foundation of the Holy City is the Pentecostal Church that began two thousand years ago on the day of pentecost when the Christians took the Gospel from Jerusalem to other parts of the world. The Holy Spirit descended on the pentecostal Christians and they went out preaching the Good News in new tongues and with all sense of confidence.
"When the day of Pentecost came, they were all in one place. Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enable them" (Acts 2:1-4)

As the history of the world advanced from the past to the future, the Pentecostal Church which began from the Acts of the Apostles transformed gradually to the Catholic church. The pentecostal Christians constitute the twelve apostles of the Lamb and the Catholic Christians constitute the twelve tribes of Israel.

This reveals that the future of the world is the past, and the past history of the world is the future of the world. When Jesus said he was going to the Father, he simply meant that he was going from the twelve apostles to the twelve tribes of Israel.
"I did come from the Father, and I came into the world; and now I am leaving the world and going to the Father" (John 16:28)
Since the Catholic Church is the 12 Tribes of Israel and the Pentecostasl Church is the 12 Apostles of the Lamb, Jesus advanced to the future by transforming from the Catholic Church to the Pentecostal Church. He came back from the future to the past by transforming from the Pentecostal Church to the Catholic Church, thus fulfilling the following promise he made to his disciples:
"When everything is ready, I will come and get you, so that you will always be with me where I am" (John 14:3)    
From the day of Pentecost, the Christian began a journey from the Jerusalem below to the Jerusalem above . The Jerusalem below was the Pentecostal Church, summarized into the twelve foundation stones (12 Apostles of the Lamb).
"The wall of the city had twelve foundations, and on them were the names of the twelve apostles of the Lamb" (Revelation 21:14)

And the Jerusalem above was the Catholic Church, summarized into the twelve gates of the New Jerusalem.
"On the gates were written the names of the twelve tribes of Israel" Revelation 21:12) 

Time (the clock) uniting the Pentecostal Church (the 12 Foundation) with the Catholic Church (the 12 gates) is the Wall of the Holy City.
"It had a great, high wall with twelve gates" (Revelation 21:12)