Abstract

Historians agree in dating back the establishment of the Vatican Observatory to 1582, the year of issue of the document Inter gravissimas, announcing the reform of the Julian Calendar by Pope Gregorius XIII. This is due to the fact that, in order to test the calendar, some astronomical observations were carried out in the Vatican, in the Tower of Winds, where a meridian line was tracked on the floor by the famous cartographer Egnatio Danti.