The Castle of San Angelo, also known as the Castle Santangelo (Castle of the Holy Angel), is a Vatican military facility in Rome, the capital of the Vatican Papal State. Located on the western side of the River Tiber, San Angelo is an ancient cylindrical building that was originally used as a mausoleum, fortress and museum. After the Armageddon, the castle was repurposed as a military fortress once more. As such, it contains the Messenger Angel Hall, otherwise known as the Vatican war room, where high-ranking political and military officials meet to discuss matters concerning the national security of the Vatican.