What does Revelation 17:9 mean?

The angel explained that the beast's seven heads are seven mountains. Many expositors attribute the seven mountains to the seven hills of Rome. Originally, Rome included seven hills on the Tiber River. These hills were named Palatine, Aventine, Caelian, Esquiline, Viminal, Quirinal, and Capitoline. Later Rome's territory included the hill Janiculum and another hill to the north.

If Rome, "the city of seven hills," is referred to in this verse, we might conclude that Rome is the beast's capital city. Or, as some do, that the religious power behind the Antichrist is connected to Catholicism. However, the following verse also refers to these seven mountains as seven kings (Revelation 17:10). It is unwise, therefore, to be dogmatic about identifying the city of Rome as the beast's capital city, or a reference to a particular religion. Just as a mountain rises above its surrounding area, so an unrighteous king or ruler exalts himself above his subjects. Further, a mountain is strong and may represent a king's political strength. In the tribulation, the beast arises as a strong political figure who exalts himself to the point of declaring that he is God and demanding that people worship him (2 Thessalonians 2:3–4).