  About fifty years after the work that astronomer Tycho Brahe carried out
while living on the island of Hven had made him world famous, King Christian IV
of Denmark built the Trinity Buildings in Copenhagen. The Tower observatory was
opened in 1642, and it housed the astronomers from the University of Copenhagen
until 1861 when a new, modern observatory was built at {\O}stervold in the
eastern part of the city. In 1996, all the University astronomers from the
observatories at {\O}stervold and the small town of Brorfelde were relocated to
the Rockefeller Buildings at {\O}sterbro, and the two observatories were
closed. In this paper we focus on the library at the observatory in
{\O}stervold, and its subsequent fate following the close-down of that
observatory.
