Heaven is both a country (Luke 19:12; Heb. 11:14-16) and a city (Heb. 11:16; 12:22; 13:14; Rev. 21:12).

The biblical truth that we will live forever as resurrected beings in a society of resurrected beings, on a resurrected earth, with our resurrected Lord, has implications that invite speculation.

Many religions, including Buddhism and Hinduism, picture the afterlife as vague and intangible. Christianity specifically refutes this notion. Biblical Christianity doesn’t give up on humanity or the earth.

The New Earth will still be Earth just as we, in our new bodies, will still be ourselves. 

Returning to the prefall-Adamic state is not our destiny. The glorification we'll experience in the resurrected state will entail the righteousness of Christ which is far beyond the innocence known by Adam and Eve. But the Curse placed on the Earth because of the fall will be removed and the natural world will have an Eden-like quality, as we see from Revelation where the Tree of Life that was in Eden will be on the New Earth.

If the New Earth is all the best of the old earth and more, then we should expect it to contain animals.

So what is “ours” is ultimately God’s, including whatever he gives to us. But that is every bit as true here on earth as it is in Heaven. And the fact that God owns whatever is “mine” does not mean there is no distinction between what I own and what others own.  

The point isn’t that God had not created the seas. The point is that the seas (or oceans) as we now know them may be radically different than the original seas

Notice that the New Jerusalem, which was in Heaven, will come down out of Heaven from God. Where does it go? To the New Earth. From that time on, “the dwelling of God” will be with redeemed mankind on Earth.