On sub level six of the Library of Illumination lies a Chamber of Doors, that can only be accessed by that library's curator. The entrance is hidden behind the stone wall of a storage room. Once a curator holds their left palm against the stone, it withdraws revealing seven doors. Each door protects a special secret.
* The uppermost level is referred to as level one.
“The cupola is the highest level, so it’s number one. Think of it like winning a prize. If you win first place, that’s the highest you can go.”
* The next level down is level two.
“…it makes sense that the window level right below it is the second level. Those massive arched windows were designed to flood the library with light, although the light in this library is sort of unearthly.”
* The third level is the halo—a single layer of shelves on a narrow balcony that overlooks the floors below.
* The fourth level is known as the residence level because it's where the curator's residence is located.
* The main floor is the fifth level.
* The basement, or cellar, is referred to as sub-level six. Below it lies sub-levels seven through 1,311.
* Nero 51's secret living compartment is located on level 333.
* Libraries of Illumination have three major staircases. The most-used one is the Curator's Steps, a circular staircase connecting the first and second floors right outside the curator's residence. Next would be the Cupola Staircase which is just off-center of the main reading room and leads directly to the cupola—five flights above. The Cupola Staircase stops at no other floors. And finally, there is the Stone Staircase, located in the front of the library just to the right of the main entrance, which connects to all levels except the cupola.