"A trip down through Manchester Central Library's stack system. Beneath the Great Hall, at the heart of the library, are four levels of library stacks (storage areas). Made of steel, they directly support the reinforced concrete floors of the building and drive down into the sandstone bedrock. They contain approximately 22 miles of shelving and were designed to provide storage space for up to one million books. The stacks contain some of the oldest and most precious treasures of the library, kept in special secure areas and an underground environment-controlled archive store"