If you go past The Bank's basement pit and the coed bathrooms you'll encounter a strange blank wall. If you speak the correct words a door will appear and a wall will swing open. Steep curving stairs lead to the lowest bowels of the building. The stairs spiral downward for what seems like miles. Another door, made of gold, ebony, and platinum, is at the bottom. INGREDIOR PERCIPIO ANIMUS is incripted around the perimeter. It's locked, a gold key will open the door.
It was a library--a large, airy space that smelled like the chalk dust and parchment. There were bookshelves that reached 75 feet to the ceiling, a maze of ladders and bridges that connexted the towering stacks. It was bright and well-lit, and decorated with cozy Aubusson rugs and Banker lamps. There are several rolltop desks.

The library files were only automated in the late 1980s. There is an ancient card catalog for anything older.

There is a private cubicle. In the back, there is a small, shabby desk. It held a gleaming iBook, several framed photographs, and a dozen Post-it notes.
The Repository held approximately ten million books. It was the largest library in the world, and the stacks went far under Manhattan, several stories below the sidewalk. No one was even sure how far down the old, rickety caged elevator went.

It's also the Headquarters. There is a boardroom behind the stacks. The Conclave of Elders- the Wardens- meet there. It's also located "right beneath Block 122", which is right next The Bank.