I for one don't care if it's a cube, pyramid, tetrahedron, or a Moebius strip. God made it for us, and I'm sure it'll be beyond anything our minds can comprehend.
In its totality, undoubtedly it will be incomprehensible; however, we can get a glimpse of what it will look like in a very general way since Yochanan's description is very general. Just the same, there are contextual clues that most miss. I choose to focus on those clues, because as tangible and as concrete as you can make it in your mind's eye, the better will be your confidence in its reality. I believe that people need to be able to visualize the city and the New Earth to increase their faith.
See, many people do not read Hebrews 11:1 correctly, and this is largely due to the way other versions render the verse.
1 Now faith is the substance of things hoped for, the evidence of things not seen.
Many hear this verse and think that faith is about the things we hope for and the things we can't see, but that is not what the verse says! Those are details in the prepositional phrases that describe the faith, but the faith itself is said to be substance and evidence! What "substance?" What "evidence?" Well, the rest of the chapter is the "evidence!" And the Holy Scriptures themselves is the "substance!" We don't have an "I hope so" kind of faith; we have an "I know so" kind of faith! Faith in God is not difficult to have, but it will always tend to elude those who don't know its nature and continue to focus on the "faith" part! If one truly wants to increase one's faith in God, the answer is simple: Get to know God! The more one understands the character of the God who can do the impossible and who truly loves His children, the easier it will be to trust Him, to have faith in Him!
It's the same thing with what to expect in our future. The more concrete our understanding of what to expect, the more likely it will be real for us and the better we'll be able to witness to others.