Uraniborg - Observatory, Laboratory and Castle

The island of Hven measures about 4.5 by 2.4 kilometres. It is a plateau with steeply rising shores, 20 - 40 meters high. On the highest point, in the middle of the island, 45 meters above the sea, Tycho in 1576 chose to construct his observatory Uraniborg.

Uraniborg was surrounded by 5.5-meter high walls, 75 meters in square. The corners were very accurately orientated in the north-south and east-west directions. The building was in the centre of a circular place, and the space between this and the outer walls was occupied by a garden of Tycho's own design. The inner garden had a strict geometric layout, and there were cultivated flowers and in particular herbs for medical and household purposes. The outer garden consisted of fruit trees.

One quarter of the garden has now been reconstructed with a good
approximation of the original vegetation. Clues came from Tycho's own records. In a other part of the garden, the museum shows 150 gardenplants known in Denmark during the renaissance. Improvement of the vegetation is carried on continuously in co-operation with the Swedish University of Agricultural Sciences.

The material in the main building was red brick, with rich decorations of sandstone and limestone. The design was inspired by Dutch architecture. The building had two main floors, one basement floor and a loft floor. On the ground floor, there was a library in southern tower, a kitchen in the northern tower, and in the square centre there were four rooms of equal size. Three of these were intended for guest researchers, the fourth was for Tycho and his family. The second floor had two smaller rooms and one large room. The large room was exclusively intended for royal guests. The basement floor had a storage room for food, salt and fuel. The rest of it was occupied by Tycho's laboratory rooms. The loft floor had 8 small rooms for students. The size of Uraniborg was rather modest: the square central body of the building was 15 by 15 meters.


However, Uraniborg was the first building ever designed with astronomical observations as its primary design criteria. The purpose of all the towers and balconies was that they should serve as instrument platforms. The orientation of the building was chosen for maximum coverage of the sky with the instruments, and to simplify the precise alignment of the great mural quadrant.

Uraniborg main building, Blaeu ´s Atlas major, 1663

The great mural quadrant was a masterpiece of simplicity and precision. It served to measure the arc height above the horizon (altitude) when the celestial objects passed the meridian plane, i.e. culminated due south.
Since Uraniborg itself was aligned exactly north-south, the fine alignment of the quadrant and the stability of the alignment were greatly simplified. With an almost 2 meter radius of the brass arc, combined with Tycho's innovative aiming device and the transversally graded scales, the instrument had a resolution of a sixth of an arc minute, i.e. 10 arc seconds. This is the absolute limit for visual readings, and only using optics is it possible to surpass this.

The laboratory in the basement was very well equipped. There were 16furnaces for chemical, medical and alchemical experiments. Some of the furnaces were connected to distillers whose cooling pipes went out of the windows and back into the laboratory. Tycho largely held the results secret, but we know that he spent most of the time developing medicines.

The great Wall Quadrant

Bird's eye view of Uraniborg
Blaeu´s Atlas major, 1663.