After a short but really important prologue set in the 2002, Tomb Raider A will start with Jerusalem, The Subdued (first real level of TR-A) when the TechnoEgyptian Empire already conquered the Surface World in the 2004.
They lived during the centuries at the Center of the World, building their Empire in ages, inside the innermost part of the Planet Earth, which is EMPTY. Like an orange you discover it has only the crust. If Ancient Egyptians were evolved the normal way since their civilization, now we will probably call them TechnoEgyptians. Exactly, TechnoEgyptians never stopped evolving, and build their superior technology and religion during the ages since they closed the way to the Center of the World with a Huge Portal.
At the Center of the Planet there is a powerful Nuclear Sun, called The Kernel, which stoked their energy for their millenary Empire. This Kernel is a Yellow Sun now near to be exhausted. It is kept alive by the energy of the Four Elements.
As you can see by the Symbol of the Planet Earth on the Load image of the game (load.bmp), Four Pylons have their foundations down the deepness of the Earth Crust on the Internal Surface, hidden to our human civilization. Those pylons collect the ENERGY for the Kernel by pluvial forests (earth), deserts (fire), and the two earth poles (water and wind).
Where on the External surface of the planet we see a desert, TechnoEgyptians on the internal one, are collecting the energy of the Fire. Where on the External Surface we see a pluvial forest, TechnoEgyptians are collecting the energy of the Earth, et cetera for the Poles.
There was a Huge War in ancient ages for the possession of the Kernel of Rhatech, the Nuclear Kernel of the Four Elements. Humans fighted the most orrible war of ever against the TechnoEgyptian Demigods, and lost. So TechnoEgyptians built a Great Legendary Portal that CLOSED forever the access to the Center of the World previously possible thanks to an Undergraound Passage near to which, Jerusalem was built. Mankind so was rejected to the External Surface and once there, forgot the Empire they were coming from, forgot the exile, forgot the Demons that lived there.
After ages, Dante's Inferno talked about this portal and the TechnoEgyptians Empire, but his interpretation was about an Hell after the death for sinners reachable from a passage exactly below Jerusalem. Instead, that passage and the Abandon Your Hope Portal were used during the centuries by TechnoEgyptians to secretly control our civilization.
In the 2002 (as the prologue in the beginning of the game tells you) Lara is in Jerusalem searching for something legendary: an ancient artefact called Imperial Symbol of New RHA. She won't find the artefact... she will meet a Father of Atlantis who will reveal to her the New RHA the Mighty prophecy: in the 2004, a future really near now, TechnoEgyptians will reveal again to Mankind who during the centuries forgot the ancient Huge War for the Conquest of the Kernel. They need to collect all the energy of the Four Elements on the Surface World, because the Kernel itself will start losing its energy on the 2004.
After they will collect enough energy, TechnoEgyptians will be ready to call again on the Earth, their wasting godness, New RHA, God of the Sun, the Internal Nuclear Sun, the Kernel. The Kernel so will be again restored for new thousands of years, their technology will be superior and powerful as never before and this means just one thing: Surface World and Mankind will be definitedly conquered after the Advent.
In the 2002 Lara listens to this Prophecy, and she is called by the Father of Atlantis to destroy the Empire before their God will be awakened again.
In the years among 2002 and 2004 she worked for this. (You have two years now, to get ready for that day, as you could hear from the first cutscene inside TR-A).
Tomb Raider A so starts with Jerusalem, The Subdued after the conquest of the Surface World: TechnoEgyptians are ALREADY collecting the FOUR ELEMENTS energy to restore the Kernel enough to have the chance to awake New RHA. You will find so Jerusalem of 2002 destroyed in the year 2004 (They are stealing our energy).
At the start, you simply are at the beginning of your search for the legendary Imperial Symbol of New RHA The Mighty.