[Rev 21:15-16 NASB] 15 The one who spoke with me had a gold measuring rod to measure the city, and its gates and its wall. 16 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, fifteen hundred miles; its length and width and height are equal.
1500 miles x 1500 miles x 1500 miles = 3.375 BILLION cubic miles.
If the population of the New Jerusalem is 10 BILLION people (more than half the total number of people that have ever lived), then each person lives in an area of about 1/3 of a mile cube.
A 216 acre house/lot that is 140 stories tall!
(sounds like a "mansion" to me.)