In the cellar of the Concertgebouw – that world famous temple of classical music – is a beautiful, round space which used to be off limits to the public. Known as the choir hall, it was always used for choruses and choirs to warm up before a concert. Recently renovated in time for Amsterdam Hidden Treasures 2008, the Koorzaal will become a jazz café every Friday evening from July 4th through August 29th 2008 and open to all visitors.