The Barbican Centre designs were approved in 1971 and included a concert hall seating 2,000, a theatre for 1,300, an art gallery, a lending library, the Guildhall School of Music and Drama, cinemas, catering facilities, foyers and car parks. The Barbican’s distinctive tooled-concrete finish is the result of an extremely labour-intensive technique. After the concrete had dried for at least 21 days, workers used handheld pick-hammers or wider bush-hammers to tool the surface and expose the coarse granite aggregate. It required great precision: pick-hammering involved pitting the surface to an average depth of 1.25 cm and bush-hammering to no more than 0.6 cm deep. The residential blocks alone necessitated over 200,000 m² of concrete to be tooled.