Passage: Rome is in the Lazio region of central Italy on the Tiber (Italian: Tevere) river. The original settlement developed on hills that faced onto a ford beside the Tiber Island, the only natural ford of the river in this area. The Rome of the Kings was built on seven hills: the Aventine Hill, the Caelian Hill, the Capitoline Hill, the Esquiline Hill, the Palatine Hill, the Quirinal Hill, and the Viminal Hill. Modern Rome is also crossed by another river, the Aniene, which flows into the Tiber north of the historic centre.

Question: How many hills were the Rome of Kings built upon?
seven hills