On May 21 1761, the Senate of the Republic of Venice issued a decree instituting an astronomical observatory at the University of Padova. This decision followed a suggestion by the Riformatori dello Studio, the Venetian magistrates responsible for the proper government of the University of Padova, and had matured within the framework of a complex program of reform of the University, with new teaching chairs and the constitution of new scientific ‘establishments’, the role of which, in modern terms, was to be that of allowing professors to ‘experiment’ and to instruct their students in the practice of experimentation.
It was not until four years later, in September 1765, that the professor of astronomy, geography and meteors, the abbé Giuseppe Toaldo (1719-97), was ordered to visit the main Italian observatories to gather information on how to build an observatory and on the instruments necessary for an astronomer’s work.
On his return, Toaldo was required to present a budget and a project, and in December 1765, the architect Don Domenico Cerato (1715-92) was summoned from the nearby city of Vicenza. Cerato was a friend of Toaldo’s and had been a fellow student with him at the episcopal Seminary at Padova, and the abbé believed, with good reason, that Cerato was one of the best architects of the time.
Giuseppe Toaldo
(1719 - 1797)

The old castle, before the transformation
As the best place on which to build the observatory, Toaldo proposed the high tower of the Castel Vecchio, the old castle, with its thick, solid walls. This tower was eminently suitable for such a transformation: in addition to allowing much money to be saved, it was on the southern outskirts of the city, and from its top the eye could range freely across the whole of the southern horizon. It was an ideal place for future astronomers to work in. And indeed, it is to the south, on the celestial meridian, that stars ‘culminate’, that is, they reach their highest position above the horizon during their apparent daily motion, and may thus be observed more easily. Thus it was that the old Medieval castle was transformed into an astronomical specola (specula is the Latin word for observatory).

South cross-section showing the transformation of the old tower in ‘Specola’.
From an original drawing by Domenico Cerato
Building work was begun in 1767 and continued for ten years.

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