Uraniborg was the astronomical/astrological observatory of Tycho Brahe; built circa 1576-1580 on Hven (also known as Ven or Hveen), an island in the Öresund; between Zealand and Scania.

Tycho Brahe's Uraniborg from his 1598 mechanica book (largest scan 320KB)

Tycho wrote that on August 8, 1576, they laid the cornerstone. The building was dedicated to Urania, the Muse of Astronomy and named Uraniborg, "The Castle of Urania."

Uraniborg became a kind of early "research institute ", which attracted students from many regions. The palace also held equipment for alchemical research, and the gardens held herbs and flowers in geometrically laid out patterns. Nearby was Tycho's subterranean Stjerneborg observatory which he built when he found Uraniborg not stable enough for his precision instruments. On losing support from the king Christian IV of Denmark Tycho abandoned Ven in 1597 and both Uraniborg and Stjerneborg were destroyed shortly after Tycho's death.

The gardens of Uraniborg are currently slowly being restored as part of a historical research project to use the species and varieties then extant.