The State Library of NSW was established in 1826 and is one of the greatest libraries in the world. This project involved the construction of a 344-seat tiered auditorium below the most iconic section of the library – The Mitchell Building Reading Room. Approximately 1000m3 of sandstone was removed to create space for the auditorium 3m below the existing lower ground floor. 93 tonnes of structural & reinforcing steel were used to support the Mitchell Reading Room & and to create the auditorium.  The totally new auditorium structure is acoustically isolated with an air plenum installed below the raked seating.  Almost all works were completed out of hours, such that the activities in the Reading Room above were not affected. Finally, the auditorium was connected to the Lower Ground Floor of the adjacent library building by a spectacular glass roofed access way. INTREC have achieved a very high-quality result from a project constructed under complex and difficult constraints.