Historical Archive of the City of Cologne up at the site of the collapse (a large hole in the ground), where around 95% of all archival items could be held until August 2011, albeit scattered and in many cases badly damaged. Archive repositories all over Germany offered space to store the damaged and only roughly cleaned documents: wet materials were flash-frozen to prevent mold growth. "Itinerant archivists" worked in the receiving archives all over the country and began the task of re-identifying and re-cataloging. A newly installed centre for restoration and digitization on the outskirts of Cologne started working in 2011, with a total cost for restoring
Cologne leading galleries for postwar and contemporary art. Several orchestras are active in the city, among them the Gürzenich Orchestra, which is also the orchestra of the Cologne Opera and the WDR Symphony Orchestra Cologne ("German State Radio Orchestra"), both based at the Cologne Philharmonic Orchestra Building (Kölner Philharmonie). Other orchestras are the Musica Antiqua Köln and the WDR Rundfunkorchester Köln, and several choirs, including the WDR Rundfunkchor Köln. Cologne was also an important hotbed for electronic music in the 1950s (Studio für elektronische Musik, Karlheinz Stockhausen) and again from the 1990s onward. The public radio and TV station WDR was