Uraniborg, Tycho Brahe's first astronomical observatory on Ven, built 1576-80 and dedicated to Urania 'The Muse of Astronomy'.
The main building of Uraniborg was square, about 15 meters on a side, and built mostly of red brick. Two semi-circular towers, one each on the north and south sides of the main building, giving the building a somewhat rectangular shape overall. The main floor consisted of four rooms, one of which was occupied by Tycho and his family, the other three for visiting astronomers. The northern tower housed the kitchens, and the southern a library. The second floor was divided into three rooms, two of equal size and one larger. The larger room was reserved for visiting royalty. On this level the towers housed the primary astronomical instruments, accessed from outside the building or from doors on this floor. Outrider towers, supported on pillars, housed additional instruments slightly further from the building, giving them a wider angle of view. On the third floor was a "loft", subdivided into eight smaller rooms for students. Only the roofs of the towers reached this level, although a single additional tower extended above the loft in the middle of the building, similar to a widow's walk, accessed via a spiral staircase from the 3rd floor. Uraniborg also featured a large basement; it housed an alchemical laboratory in one end, and storage for food, salt and fuel at the other.
A large wall, 75 meters on a side and 5.5 meters high was planned to surround Uraniborg, but never built, instead a high earth mound was constructed and lasted until today being the only remain of the observatory still in place. Uraniborg was located in the very middle, with an extensive set of intricate gardens between the mound walls and the building. In addition to being decorative, the gardens also supplied herbs for the Tycho's medicinal chemistry experiments. The gardens are currently being re-created, using seeds found on-site or identified in Tycho's writings.