Judenplatz Holocaust Memorial
The Judenplatz Holocaust Memorial is in Vienna, Austria. The Judenplatz itself has been a site of many events that are a part of Jewish history, including the burning of a Synagogue during the Progroms of 1420.
The memorial, designed by British artist and sculptor, Rachel Whiteread, is the insides of a library. The concrete memorial shows the negative space, representing the lost knowledge and intellectual contributions that could have been made by those who were killed during the Holocaust.
http://www.sacred-destinations.com/austria/vienna-judenplatz.htm

