Revelation 21:16

The city is laid out as a square
Although the land dedicated for the millennial city had the dimensions of five thousand cubits wide and twenty-five thousand cubits long (Eze. Eze. 45:6), the portion where the city itself stood was, like the eternal city, also square: four thousand five hundred cubits on a side (Eze. Eze. 48:16, Eze. 48:30-35).

twelve thousand furlongs
Furlongs is σταδίων [stadiōn] , each of which is equivalent to 400 cubits or 1/8 mile. The dimension is equivalent to 4,800,000 cubits or approximately 1,500 miles.1 Morris takes the stadia as 600 Greek feet or approximately 607 English feet resulting in a dimension of 1,380 miles.2

The city itself is gargantuan; it is a cube of 12,000 stadia (i.e., with sides of 1,380 miles each [depending upon the value taken for 1 stadia]). Now, the base of the city is staggering enough, for its area is 63% of that of the forty-eight contiguous states of the USA, yet it is 1,380 miles high as well. Now, as we are given no details, we cannot say what significance the height has, but by way of comparison, this city would only need 102 levels to equal the surface area of the earth, i.e., the combined areas of the oceans and the land masses (this last figure would require each level to be separated by 70,000 feet, considerably higher than commercial jet airplanes operate in 1998). These hypothetical 102 levels would have a combined area 340% larger than the total land area, deserts and vast frozen wastes included, of the present earth. The point of all this comparison is to emphasize that the city God describes is actually many times more commodious than the earth we know.3

Its length, breadth, and height are equal.
The eternal city is over 1,060 times larger in each dimension than the millennial city proper and has a total square area over 1.1 million times larger. The gargantuan proportions of the city are such that many seem unable to take them as the description of a literal city. But how is this huge city any more difficult to believe than a totally new heaven and earth (Rev. Rev. 21:1+)? And how often is skepticism over God’s prophecy based on our limited experience in the present reality—none of which need attend the scene before us? The equal dimensions of the city recall the holy of holies in the Temple where the ark of the covenant resided, which was twenty cubits long, twenty cubits wide, and twenty cubits high (1K. 1K. 6:19). The entire New Jerusalem is the eternal “holy of holies” (Rev. Rev. 21:22+). For a detailed estimate of the ability of the city to accommodate the redeemed of history, see [Morris, The Revelation Record].

Notes

1 Trent C. Butler, Chad Brand, Charles Draper, and Archie England, eds., Broadman and Holman Illustrated Bible Dictionary (Nashville, TN: Broadman and Holman Publishers, 2003), 1666.

2 Henry Morris, The Revelation Record (Wheaton, IL: Tyndale House Publishers, 1983), Rev. 21:16.

3 Monty S. Mills, Revelations: An Exegetical Study of the Revelation to John (Dallas, TX: 3E Ministries, 1987), Rev. 21:16.

4 Morris, The Revelation Record.

Read Revelation 21:16