The spectacular Galleria delle Carte Geografiche (Gallery of the Maps) was commissioned by Pope Gregory XIII (r. 1572-85) and designed by Egnazio Danti (1536-86), Dominican priest, cosmographer and mathematician.
The gallery, which is 120 metres long, was designed and built by Ottaviano Mascherino (1536-1606) between 1578 and 1579. It was painted between 1579 and 1581 with a series of maps of the regions of the Italian peninsula, its neighbouring islands, its most important ports, and the papal territory of Avignon.
Danti designed and prepared the cartoons of the 40 maps, each of which contain a scale, a wind-rose, and the coordinates of latitude and longitude.
The frescoes on the vault illustrate events in the history of the church that happened in the territory mapped below on the walls, a marriage of history and geography. The paintings were planned by Girolamo Muziano (c.1532-92) and Cesare Nebbia (c.1536 - c.1622) and executed by a team of artists.
The maps of ancient and modern Italy are connected with five scenes on the vault, which illustrate episodes from the life of the emperor Constantine the Great (r. 306-337), the only figure to be represented so extensively in the gallery.
The gallery was restored in 1630, on the orders of Pope Urban VIII (r. 1623-44), who had his family's heraldic charge, the bee, added to many of the maps.