We have a problem with understanding the heavenly realm because we live in a three dimensional world (four, if time is included). All our categories of thought are shaped by the world in which we live. Our language is inadequate for describing the spiritual dimension to life. The New Testament uses physical images to describe the spiritual dimension, but these will always be inadequate to describe something that is beyond description.No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him (1 Cor 2:9).
Our human minds are not even capable of understanding what this universe looks like when perceived from the spiritual dimension as God sees it.
When we think of heaven, we tend to think of a place where God dwells. The problem is that God is spirit, so he is not confined to one place. The heavenly realm is not a three dimensional world like the one we live in, so the idea of “being somewhere” does not mean what it means here on earth. The same applies to expressions like “third heaven” or “highest heaven”. These phrases do not mean that the heavenly realm has layers like a multi-level building. Up and down do not mean the same in a spiritual world as they mean in this physical world. The expression “highest heaven” is just an attempt to describe the total difference between the physical world and the spiritual world.
The description of the heaven realm in Revelation 21 should be understood in the same way.The angel who talked with me had a measuring rod of gold to measure the city, its gates and its walls. The city was laid out like a square, as long as it was wide. He measured the city with the rod and found it to be 12,000 stadia in length, and as wide and high as it is long. He measured its wall and it was 144 cubits thick, by man's measurement, which the angel was using (Rev 21:15-18).
John is trying to describe the wonder of the spiritual realm using human words, but they are inadequate for this purpose, so we need to be careful how we interpret them. Length, width and height will not mean much in the spiritual world, so they should not be taken as a literal description. The walls were 144 cubits thick by “man’s measurement”, but thickness does not really mean anything in the spiritual world. Jesus proved this when he appeared to the disciples hiding behind physical walls in a locked room after his resurrection. Thick walls could not keep Jesus out.
John reminds are that these dimensions are “man’s measurement”. He is using human categories of thought so that he can communicate to us, because that is all we can understand, but earthly categories cannot fully capture the glory of the heavenly realm.The wall was made of jasper, and the city of pure gold, as pure as glass. The foundations of the city walls were decorated with every kind of precious stone. The first foundation was jasper, the second sapphire, the third chalcedony, the fourth emerald, the fifth sardonyx, the sixth carnelian, the seventh chrysolite, the eighth beryl, the ninth topaz, the tenth chrysoprase, the eleventh jacinth, and the twelfth amethyst. The twelve gates were twelve pearls, each gate made of a single pearl. The great street of the city was of pure gold, like transparent glass (Rev 21:19-21).
I doubt that gold and emeralds will have much value in the future life. Peace and love and truth will be the important values. The problem is that the human mind cannot conceive of a place where love and peace have replaced height and width as the core dimensions. Using precious jewels was a way of describing the indescribable using things of value to a human mind.