One aspect of Janet Willis’s writings has shown with clarity in her What On Earth Is Heaven Like? A Look at God’s City: New Jerusalem that interpreters have assumed a linear measurement rather than considering a cube measurement. She explains all of this in Chapter 3 of her book. If for no other reason purchase the book for this chapter!
The book also contains other fascinating commentary on the location of the New Jerusalem, the location of the temple in relationship to the New Jerusalem, the timing of the New Jerusalem in relation to the millennium, what a mountain has to do with Eden and the New Jerusalem, and other features of the New Jerusalem.