The last two chapters in the book of Revelation reveal the Good news that follows all of the Bad News of the prior few chapters. John brings together symbols from Genesis to the Prophets to describe the perfect world beyond the terrible judgments of God upon all sin and sinners. The main symbol is the Heavenly Jerusalem, which comes down from God´s own dwelling place, heaven.
This city is the absolute opposite of everything Rome and Babylon truly stood for. This is the place of true peace and harmony that results from the mission of Jesus Christ to redeem humanity. All that has gone before it is ashes. Rome had no glory to even compare!
The river and the tree of life are images from Genesis, symbolizing a brand new creation. The only thing in common with the original creation is the redeemed humanity that Jesus brought with Him into this paradise. The Tree of Life is freely accessible for the first time since Adam and Eve were exiled from the original Garden of Eden. (Remember that their exile from the garden was precisely to cut humanity off from eternal life via the Tree of Life in Genesis 3.)
These chapters are symbols of humanity restored to the life and balance they were intended to have at the beginning of creation. They are now lords over creation, under God and His Son. This future harmony and balance are available freely to any who would embrace Jesus Christ as Saviour and Lord.
These symbols have been embraced by Christians across the centuries for the hope they give in troubled times of war and oppression at the hands of evil kingdoms. We too can embrace the hope in this generation as societies around us ebb and flow, and inevitably decline into violence and corruption.
Followers of Jesus Christ, hold on to the vision at the end of the book, and all will be well. Stay faithful to your Lord and Saviour!