Revelation 21:16

ESV The city lies foursquare, its length the same as its width. And he measured the city with his rod, 12,000 stadia. Its length and width and height are equal.
NIV 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.
NASB The city is laid out as a square, and its length is as great as the width; and he measured the city with the rod, twelve thousand stadia; its length, width, and height are equal.
CSB The city is laid out in a square; its length and width are the same. He measured the city with the rod at 12,000 stadia. Its length, width, and height are equal.
NLT When he measured it, he found it was a square, as wide as it was long. In fact, its length and width and height were each 1,400 miles.
KJV 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.

What does Revelation 21:16 mean?

The dimensions given here for New Jerusalem are at once specific and yet vague. The description given here gives size, but not shape—so this might be describing a cube, or a pyramid. The city "lies foursquare", so its base is square. Its length and width are equal, each measuring 12,000 stadia or approximately 1,400 miles (2,250 km), about the distance from New York City to Dallas, Texas. The area of the base is about 1,960,000 square miles (more than 5 million square km).

The city's height—either the tallest buildings or the top of some foundational structure—is also 12,000 stadia or about 1,400 miles (2,250 km). The question of whether the city is a cube or a pyramid is debatable. Typical architecture of John's era would have used a pyramid shape rather than a simple cube for something like a city. However, regardless of its shape, the presence of oceans, lakes, rivers, and streams on the millennial earth seems to suggest the earth could not accommodate such a large city. The new earth has no sea (Revelation 21:1), so some scholars suggest New Jerusalem hovers like a satellite city over the millennial earth but descends to the new earth (Revelation 21:10) after the millennium.

One thing is certain: New Jerusalem is large enough to accommodate all believers saved throughout all of history. The dimensions of New Jerusalem, whether cubic or pyramidal, are enough to provide ample room for billions upon billions of people. Whereas most ancient cities just grew without planning, New Jerusalem follows the plan of God, its Master Builder.
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