Across from the Detroit Institute of Arts, you will find the main
branch of the Detroit Public Library.
According to wikipedia, it's the 20th largest library system in the country, and the second largest in the state of Michigan (UofM is first).
One of the best features of the library is its "Double Imperial Staircases'. Imperial staircases feature a single staircase going to a landing part of the way up. It then splits and goes to the final level via two separate staircases. DPL is REALLY special because it has two of these back to back.