Subtropical Cyrodiil : A Speculation Content . According to " The Heartland of Cyrodiil , " by that old fraud Phrastus of Elinhir , the Nibenese valley and the Colovian hills have always enjoyed the temperate climate they have today , and early references to Cyrodiil as a subtropical jungle were merely errors on the part of one of the Heimskrs . Really ? What , then , of the " waving fronds " of Vahtacen mentioned in the Hosiric Lays ? What of Khosey ' s " dense - jungl ' d shore of Rumare " in the Tamrilean Tractates ? Are these , as well , the mistakes of errant copyists ? No , I think it more likely that three millennia ago Cyrodiil ' s climate was warmer and wetter than it is today . The environment of the Heartland has changed . Which begs the question : how ? I ' ve given a great deal of thought to this question , and would like to propose a hypothesis . However , I am not a scholar of deep mythohistory like Vanus Galerion or Beredalmo the Signifier , so let ' s just call the following . . . a speculation . Tamriel is the center of Nirn ; Cyrodiil is the center of Tamriel ; and at the center of Cyrodiil stands that greatest of mortal - made structures , the White - Gold Tower of the Imperial City — which was patterned in open emulation of the Adamantine ( or Direnni ) Tower , the oldest structure in Tamriel , said to have been erected by the Aedra themselves . This was no mere homage , whim , or coincidence : White - Gold was built in the semblance of Adamantine in order to echo the first Tower ' s undeniable mystical properties . And not just to echo them , but , due to its central location , to amplify them . What are these mystical properties ? This leads us to the domain of Tower Lore , a realm fraught with scholarly conflict , but I will try to give a simple , and uncontroversial , summary . When the Aedra were persuaded — or hoodwinked — by Lorkhan into creation of the Mundus , the physical flesh of Nirn was hung on a skeleton of joints , each of which radiated a palpable reality — the bones of the world , as it were . At one of these mystical joint - points the Aedra erected a great structure , the Adamantine Tower , where they held a conclave to decide the fate of Lorkhan and the Mundus . In later times mortal mages discovered the Tower , and deduced its reality - affirming properties . The Merethic Elves then imitated it , erecting the White - Gold and Crystal Towers at other joint - points . In doing this , what did the Ur - Elves hope to achieve ? I would posit that , through their collective " possession " of such Towers in their realms , over time the Elves actually amended their local reality to conform to their desires . Thus the Summerset archipelago , in the sphere of the Crystal Tower , is a warm and paradisiacal domain perfectly adapted to the Altmer . And Cyrodiil , in the sphere of the even - more - powerful White - Gold Tower , became a warm and subtropical jungle — which suited the ease - loving Ayleid s . But then the slaves of the Heartland High Elves rose up against their masters , conquered the valley of the Nibenay , and the Ayleids ruled no more . Thereafter , White - Gold Tower was the center of a human empire , peopled by Nede s and Cyro - Nord s who originated in cooler , northern climes . And so the Tower of Cyrodiil responded to the desires of its new masters . And that , I believe , is the answer to how the Heartland changed from subtropical to temperate : because once Men ruled in Cyrodiil , the local reality changed to meet their needs and wishes . Changed slowly , perhaps , almost imperceptibly , but inexorably — until Cyrodiil became the realm of temperate forests and fields we now know . So , is that the truth of the matter ? Have I deduced the answer to the mystery ? I cannot be sure : I ' m only a humble scholar , residing in the Tower of the Fifth Doctrine , which is neither White - Gold nor Adamantine Tower . The only thing I ' m quite sure of is that any theory propounded by Phrastus of Elinhir is almost certain to be wrong .