“All its dimensions were equal”
The city lies foursquare, with its width the same as its length. And he measured the city with the rod, and all its dimensions were equal, 12,000 stadia in length and width and height. (Revelation 21:16 BSB)
What it sounds like today
Strange architecture: a cube-shaped city.
The cultural key
Scripture contains exactly one other cube: the Holy of Holies, twenty cubits by twenty by twenty (1 Kings 6:20), the gold-lined inner room entered by one man on one day a year. The new Jerusalem is that room scaled to continental size (12,000 stadia is roughly the distance from Jerusalem to Spain), which is why the next lines report what every ancient reader would ask about first: 'I saw no temple in the city, for its temple is the Lord God the Almighty and the Lamb.'
Recovered meaning
The city does not contain a Holy of Holies; it is one. The entire redeemed world becomes the innermost room, the space behind the veil (torn at the crucifixion, entered by the forerunner), now the address of everyone. The Bible's last architecture answers its oldest exclusion.