Revelation 21:15-17

The angel who spoke with me had a gold measuring rod to measure the city, its gates and walls. The city was laid out in a perfect square; its length, width, and height were equal. So he measured the city with his rod, and it was 12,000 stadia, with equal dimensions for its width, length, and height. He also measured the wall at 144 cubits, according to the measure of a man, which is angelic.