The Tower is unique: a colossal cylindrical megastructure of interlocking structures extending far above the clouds. People speak of roughly 100 floors, but this is unreliable.
Amended D-300 It is only ever called "the Tower". It has no proper name: not "the White Tower", nor any other.
Floors are gameplay progression, not architectural layers. A stair, void, column, platform or chamber may cross many gameplay floors.
Routes include intact architecture, ruins, climbing, previous expedition infrastructure, bridges, balconies, exterior passages and private shortcuts. The Tower is believed to change, but nobody sees the change happen.
Amended D-303 The Pressure (§28) comes closest: the surroundings seem to close in and collapse, and afterwards everything is as it was.