Revelation 21:11-14

11  Having the glory of God: and her light was like unto a stone most precious, even like a jasper stone, clear as crystal;

12  And had a wall great and high, and had twelve gates, and at the gates twelve angels, and names written thereon, which are the names of the twelve tribes of the children of Israel:

13  On the east three gates; on the north three gates; on the south three gates; and on the west three gates.

14  And the wall of the city had twelve foundations, and in them the names of the twelve apostles of the Lamb.

Some like to make this structure the bride of Christ but  what is being described is a city of great beauty that reflects the beauty of the redeemed of the commonwealth of Israel within her. John was looking at this city and describing what he saw. The city is of supernatural design. The names of the twelve tribes of Israel are written on the gates and the names of the twelve apostles are written on the twelve foundations. Nowhere does it say that the gates and foundations are actually those twenty-four men. The gates of the city will be a testament forever that salvation is through the Jews.  This is what Jesus told the woman at the well.

John 4:22   Ye worship ye know not what: we know what we worship:  for salvation is of the Jews.

23  But the hour cometh, and now is, when the true worshippers shall worship the Father in spirit and in truth: for the Father seeketh such to worship him.

24  God is a Spirit: and they that worship him must worship him in spirit and in truth.

The access to the city is only through the gates of Israel;  angels protect the gates (not St. Peter). The names on the foundations tell us that the saved in the city live on the teachings laid by the apostles. The city has three gates on each side and is four square in design.

The foursquare design speaks of God’s incarnation on earth as Messiah, Servant, Man, and Son of God. We also see this in the four creatures that surround His throne that have a face of a Lion, Ox, Man and Eagle. Even the four gospels of his sojourn on earth are written to reflect this truth. Matthew’s emphasis is that Jesus is the Messiah, the Lion from the tribe of Judah (Lion); Mark’s emphasis is that Jesus came as a suffering servant (ox); Luke’s emphasis speaks of Jesus coming as the son of man (man); and John’s emphasis tells of Jesus’ heavenly origin (eagle).