Vatican City isn’t built on seven hills, and the hill it is built on wasn’t one of the seven hills of ancient Rome, all of which are on the opposite side of the Tiber.
Ancient Jerusalem, however, like ancient Rome, was noted as a city built on seven hills
Catholic apologist Karl Keating confirms that Rome was known as Babylon and cites 1 Peter:5:13 The church that is at Babylon, elected together with you, saluteth you; and so doth Marcus my son.. 1 The Catholic Encyclopedia states, “It is within the city of Rome, called the city of seven hills, that the entire area of Vatican State proper is now confined.” [The Catholic Encyclopedia ( Thomas Nelson, 1976), under the heading, “Rome.”]