Revelation 21:14 And the wall of the city had twelve foundations, and in them the names of the twelve apostles of the Lamb.
15 And he that talked with me had a golden reed to measure the city, and the gates thereof, and the wall thereof.
16 And the city lieth foursquare, and the length is as large as the breadth: and he measured the city with the reed, twelve thousand furlongs. The length and the breadth and the height of it are equal.
17 And he measured the wall thereof, an hundred and forty and four cubits, according to the measure of a man, that is, of the angel.
As the angel continued showing and telling John about the city he showed him the twelve foundations which were named after the twelve apostles, the same twelve apostles that the foundation of Christianity was built on. Now the angel had a golden measuring stick to measure the city, gates , and wall . The city itself was a perfect cube, because God built and designed it, it was 1500 miles on each wall and 1500 miles high. Remember how the walls of the city in ancient times were wide enough to race chariots around on them, well these walls are 216 feet across, just a tad wider. There is more to the walls but I wanted to stop here so we can truly understand the greatness of the the construction of this city.