Uraniborg

the observatory of the Danish astronomer Tycho Brahe, built in 1576 on the island of Hven (now Ven) in the strait of Øresund near Copenhagen. The observatory was in effect a castle, the first structure in Europe intended specifically for astronomical observations. It was equipped with excellent instruments for its time, designed by Tycho himself and made in the Uraniborg workshops. Among the instruments was a large wall quadrant, with which Tycho determined the position of stars and planets with an accuracy no one else could surpass with the naked eye. After Tycho left Denmark in 1597, Uraniborg and his second observatory, Stjerneborg, were abandoned.