The Vatican Observatory is an astronomical research and educational institution supported by the Holy See. Originally based in the Roman College of Rome, the Observatory is now headquartered in Castel Gandolfo, Italy and operates a telescope at the Mount Graham International Observatory in the United States.

Castel Gandolfo, colloquially known as Castello in the Castelli Romani dialects, is a town located 25 km (16 mi) southeast of Rome, in the Italian region of Lazio. Situated on a hilltop in the Alban Hills with panoramic views of Lake Albano, Castel Gandolfo is home to approximately 8,900 residents and is renowned as one of Italy's most scenic towns. It is one of I Borghi più belli d'Italia.