It was clear that the mana the elemental spirits were bringing toward the tower was having a great effect. Once Walker got to the top of the tower, he was able to look out over all of Genesis and sense the mana coming toward it.
What was even more evident was that the mana was being condensed and balancing the elemental floors. The runes that reached the top of the mage tower were glowing brilliantly while releasing more condensed mana in to the air. This was how the tower was able to influence the entire city.
When Walker and Fleur were near the central point of the tower, they found a single rune that was more intricate than any of the other runes. This was something that Walker had not sensed nor seen anywhere else in the mage tower.