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.
Revelation 21:9–27 presents a description of the New Jerusalem. Interpreters disagree about whether this is a flashback to the millennial reign of Christ, or a description of the eternal state of the city. A flashback is not unprecedented in Revelation, occurring in chapters 11, 14, 15, and 17. However, some verses here clearly refer to eternal conditions, and most scholars take this as a depiction of the eternal, final heavenly city.
This chapter focuses on the New Jerusalem. This is not the earthly, historic Jerusalem of the tribulation (Revelation 11:2, 8). Nor is it the surviving Jerusalem of the millennium that serves as Jesus' capital (Revelation 20:9). It is the heavenly city referred to in Hebrews 12:22, whose designer and builder is God (Hebrews 11:10, 16). John attempts to describe the indescribable using analogies to precious gems and metals.