How many hills form the geographical heart of Rome?

The seven hills of Rome east of the river Tiber form the geographical heart of Rome, within the walls of the city.

The seven hills are:

Aventine Hill

Caelian Hill

Capitoline Hill

Esquiline Hill

Palatine Hill

Quirinal Hill

Viminal Hill

Tradition holds that Romulus and Remus founded the original city on the Palatine Hill on April 21, 753 BC, and that the seven hills were first occupied by small settlements that were not grouped. The seven hills' denizens began to interact, which began to bond the groups. The city of Rome, thus, came into being as these separate settlements acted as a group, draining the marshy valleys between them and turning them into markets (fora in Latin). Later, in the early 4th century BC, the Servian Walls were constructed to protect the seven hills.

In modern Rome, five of the seven hills, the Aventine, Caelian, Esquiline, Quirinal, and Viminal Hills, are now the sites of monuments, buildings, and parks. The Capitoline Hill is the location of Rome's city hall, and the Palatine Hill is part of the main archaeological area.