Astronomical Observatory of Padova, Astronomical museum and observatory in Padua, Italy

La Specola is the observatory of Padua, built into the Torlonga, the tall square brick tower of the old Castelvecchio beside the Bacchiglione. The tower rises 49.59 metres, with a crown of corbels under a projecting top; an octagonal upper room with tall windows sits at the summit, and a lower meridian room lies 16 metres above ground. A dark wooden cylindrical structure clads the tower's right base.

The Torlonga was a defensive tower built in the 9th century and reworked by Ezzelino III da Romano in the 13th century, who used it as a prison and torture chamber for his enemies. The Carraresi raised it further in the 14th century. In 1761 the Venetian Senate decreed an observatory for the University of Padua; Giuseppe Toaldo and architect Domenico Cerato converted the tower, completed in 1777.

The upper octagonal hall was frescoed between September 1772 and August 1773 by the Vicentine painter Giacomo Ciesa, with astronomical subjects devised by abbot Giuseppe Toaldo. The museum keeps these frescoes, portraits of astronomers and a collection of 18th-century instruments: quadrants, refracting telescopes and pendulum clocks. Above the ground-floor door a 1777 plaque marks the tower's change from prison to observatory.

The tower stands on the Castelvecchio beside the Bacchiglione, entered from Piazza Castello. The 252 steps to the top are climbed on foot, and the octagonal upper room is reached after the lower Sala Meridiana at 16 m. The museum section occupies the former Casa del Munizioniere, once the prison infirmary under Austrian rule.

The Meridian Room features a meridian line engraved on the floor that helped astronomers track celestial bodies as they crossed the local meridian. This method was an important way to determine exact positions of stars and planets.