It had a GREAT and HIGH WALL,
A GREAT and HIGH WALL indicates the new Jerusalem will provide supreme protection for Christ and His Wife. The size of the wall is given in verse 17. It sounds like a GREAT WALL, and yet in comparison to the size of the city (verse 16), the GREAT WALLS are relatively small. In previous verses, the new Jerusalem was depicted more in spiritual terms, e.g. the holy city (verse 10) and {the city} having the GLORY of GOD (previous verse).
When we read Zechariah 2:1-5-5, it appears as though the prophet Zechariah is seeing the same thing that John is describing here. However, in Zechariah's description, the WALL is the Lord himself and the WALL is described as a WALL of fire. This description fits very nicely with the BRILLIANCE of the previous verse.
with twelve GATES, and at the GATES twelve ANGELS; and NAMES were written on them, which are those of the twelve TRIBES of the SONS of ISRAEL.
GATES are the places where people intermingle as some are entering the holy city, while others are leaving the holy city. It might seem strange to have ANGELS at the 12 GATES as gatekeepers. In the Old Testament, it was considered an honor to be counted as one of the gatekeepers. These ANGELS were specifically assigned one to each of the 12 TRIBES of the SONS of ISRAEL. This shows us that the covenant made with Abram (Genesis 12:1-3) is an everlasting covenant and has carried through to the new Jerusalem. GOD KEEPS HIS PROMISES!
Angels also are messengers. At the beginning of this study, we found that ANGELS were messengers, one assigned to each of the seven churches (Revelation 1:20). In this verse, we may wonder what kind of messages are these ANGELS carrying? With the foundations of the WALL allocated to the 12 apostles (verse 14), perhaps the angels are sharing the love of God between the Jews signified by the twelve TRIBES of the SONS of ISRAEL and the non-Jews signified by the twelve apostles. Personally, as a non-Jewish believer, I would very much like to know about the covenant that the Jews have with God. It is unique. Just listen to the evening news, and you soon realize that the world understands the significance of ISRAEL too.
GATES also appear to have a special meaning to God. In Psalm 87:2, we see that the Lord loves the GATES of Zion, and in Psalm 118:19-21, the GATES are GATES of RIGHTEOUSNESS. The new Jerusalem is a place of RIGHTEOUSNESS that the Lord loves. In Ezekiel 48:30-35, Ezekiel calls the city, "The Lord is there" (see previous verse - 'having the GLORY of GOD"), and Ezekiel gives the specific names for each of the GATES.