Tower of Winds, Vatican. Built in 1578 and 1580 the impressive hall has a special purpose: it was made to proceed with astronomical studies and reform the Calender.
The area of two floors was made by architect Ottaviano Mascherino and later frescoed by the brothers Paul and Matthijs Bril, Simone Lagi and other artists. The space is decorated with gorgeous frescoes, that feature Biblical scenes or Italian landscapes.
Meridian Hall is especially exciting: on 21 March a solar phenomenon occurs, when the sunray hits a tiny hole in the wall and illuminates an astronomical constellation on the floor. Tower of Winds is part of the Vatican Secret Archives and is used in official occasions only.