10. In the twenty-first chapter of Revelation we find the following description of the holy Jerusalem:

Its light was like a most precious stone, like a jasper stone, clear as crystal. It had a great and high wall with twelve gates, and on the gates were twelve angels and the names written of the twelve tribes of the children of Israel. Its wall measured one hundred and forty-four cubits, which is the measure of a human being, that is, of an angel. The construction of its wall was of jasper, and its foundations were made of precious stones of every kind - jasper, sapphire, chalcedony, emerald, onyx, sardius, chrysolite, beryl, topaz, chrysoprase, jacinth, and amethyst. The twelve gates were twelve pearls. The city was pure gold, like clear glass, and was square - its length, breadth, and height were equal at twelve thousand stadia each. [Revelation 21:11-12, 16-21]

And so on.

We can tell that all these features are to be understood spiritually from the fact that the holy Jerusalem means a new church that the Lord is going to establish, as explained in §§62-65 of Teachings on the Lord. Further, since Jerusalem here means the church, it follows that everything said about it - about the city, its gates, its wall, the foundations of the wall, and its dimensions - has spiritual meaning in it, since what goes to make up the church is spiritual.

As for the meaning of the details, though, these have been explained in §1 of The New Jerusalem and Its Heavenly Teachings (published in London in 1758), so I forego further explanation.

Suffice it to say that we know from these examples that there is spiritual meaning in the details of the description of the city, like a soul within a body, and that if it were not for this meaning we would find nothing relevant to the church in what is written there - the city being of pure gold, the gates of pearls, the wall of jasper, the foundations of the wall of precious stones; the wall measuring a hundred and forty-four cubits by the measure of a human being, that is, of an angel; the city itself being twelve thousand stadia in length, breadth, and height; and so on.

Yet people who are familiar with the spiritual meaning because of their knowledge of correspondences understand that the wall and its foundations mean a body of teaching drawn from the literal meaning of the Word, and that the numbers twelve, a hundred and forty-four, and twelve thousand all mean much the same, namely, all the good and true features of the church viewed in one combined form.