The Papal Palace of Castel Gandolfo, or the Apostolic Palace of Castel Gandolfo from its Italian name Palazzo Apostolico di Castel Gandolfo, is a 135-acre complex of buildings in a garden setting in the city of Castel Gandolfo, Italy, including the principal 17th-century villa, an observatory and a farmhouse with 75 acres of farmland. The main structure, the Papal Palace, has been a museum since October 2016. It served for centuries as a summer residence and vacation retreat for the pope, the leader of the Catholic Church, and is afforded extraterritorial status as one of the properties of the Holy See. It overlooks Lake Albano.