The Moon. The Catholic Church is the spiritual heir to the Roman Empire, although since the 1860s its temporal power has been sadly circumscribed. According to the Code of Canon Law, any newly-discovered territory falls under the jurisdiction of the bishop from whose diocese the expedition set out. Since the Apollo space mission set out from Cape Canaveral in the Diocese of Orlando, this means that the Moon falls under the jurisdiction of the Bishop of Orlando. (No, really.) So the Moon falls under the jurisdiction of a bishop of the Catholic Church, and, since there are no civil authorities currently claiming control over the satellite, the Church's power there is not circumscribed either spiritually or temporally. Hence the Moon is where the writ of the heir to the Roman Empire most truly applies, and the Moon is of all places the one that can most properly be considered part of the Roman domains.