The Seven hills of Rome are somewhat problematic to identify since there are more than seven historic hills. Even the ancient authors debated which of the hills constituted the seven, in regard to the discussion of the festival of the Septimontium. So we don't really need to get into a heated debate about the "correct" seven! Volcanic eruptions are a factor in Italy's formation. Monte Albano in Lazio (southeast of Rome) is the area that most affected Rome and its formation. Eruptions deposited ash or tuff, thereby constituting the hills of Rome. The local water supply (aquifers, streams) were greatly influential on the city, determining where people lived (e.g., Forum Romanum). The tuff hills of Rome (just big deposits of ash 35-45 meters high) were protective but lacked natural water supplies, so water had to be collected in cisterns or located nearby. The Tiber River, whose course has changed over time, was not just Rome's lifeline to the Mediterranean but an important supply of water as well. Its earlier course is known as the Paleotiber. For further reading: G. Heiken, R. Funiciello, R., D. Rita, The Seven Hills of Rome: A Geological Tour of the Eternal City. This content is brought to you by The American Institute for Roman Culture (AIRC), a 501(C)3 US Non-Profit Organization. Please support our mission to aid learning and understanding of ancient Rome through free-to-access content by donating today via the following link: https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=T44AE774MKBJE&source=url Don't forget also to subscribe, comment and like! You can also support us by following and engaging across our social media channels: Twitter: https://twitter.com/saverome Facebook: https://www.facebook.com/AIRCSaveRome/ Instagram: http://instagram.com/saverome/