The memorial the Empty Library, by Israeli artist Micha Ullman, is located on one of the sites of the many Nazi book burnings in 1933. The installation commemorates a book burning staged by students and faculty of nearby Humboldt University before a large audience at the university's Old Library. The books were mainly by Jewish, Communist, liberal, and socially critical authors. The memorials empty bookshelves, sunken into the ground and painted stark white, are large enough to hold the estimated 20,000 books burnt by the Nazis. A nearby plaque with words from a play by the poet Heinrich Heine states, that was but a prelude / where they burn books / they will ultimately burn people as well.