“And here is the mind which hath wisdom. The seven heads are seven mountains, on which the woman sitteth.”
King James Version (KJV)
17:9 Here is the mind that hath wisdom - Only those who are wise will understand this. The seven heads are seven hills.
Re 17:9 Here [is] the mind which hath wisdom. The mind that hath wisdom can interpret what follows. The seven heads are seven mountains. Since just one city in the world was called the city of seven mountains ("septem montes") in John's time, there must be a reference to that city.