Gregorian Tower

The Gregorian Tower is an astronomical tower in Vatican City that rises above the Gallery of Maps with two main floors, a mezzanine, and a square base structure holding scientific instruments. The tower preserves its original meridian line and various measurement devices from the Renaissance period.

The tower was built between 1578 and 1580 by architect Ottaviano Mascherino to support astronomical studies for implementing the Gregorian Calendar Reform. Later under Pope Urban VIII, the loggia was transformed into an observation platform and the building was expanded.

The Sundial Room displays detailed frescoes by Flemish artists Paul and Matthijs Bril showing biblical scenes and landscapes. These rooms were used by cardinal librarians, reflecting how scientific and religious studies came together in this space.

Access is through the Vatican Museums, and visitors should expect average to busy conditions, particularly in warmer months. The rooms are connected by narrow stairs and several steps, which can be challenging for people with mobility issues.

The tower's original meridian line was hidden for decades and only rediscovered during modern restoration work. This line served as a precise measuring instrument for astronomical observations and reveals the level of scientific accuracy achieved during the Renaissance.