The Capitoline Hill is the smallest of Rome's famous seven hills, but also the most important. Finds dating back to the Bronze Age (around 1300 BC) testify that the Capitoline Hill was inhabited long before the founding of Rome. Two heights, the Arx and the Capitolium, originally characterized the hill, separated by a small depression, the Asylum, where the first king Romulus welcomed the inhabitants of the nearby towns. The name of the hill derives from the temple of Capitoline Jupiter (Capitolium); According to another tradition, the name Capitoline derives from the discovery of the head (caput) of an Etruscan warrior, Aulus Vipsania: caput Auli, hence Capitolium.

During the Middle Ages, the Capitoline Hill was gradually abandoned, so much so that it was used for goat grazing, thus being called "Monte Caprino." Pope Paul III Farnese, in anticipation of the visit of Emperor Charles V to Rome, commissioned Michelangelo to design a new square, Piazza del Campidoglio.

Michelangelo designed an imposing staircase with wide steps for access to the square, the "Cordonata," which allowed even horsemen to ascend easily. It culminated with a balustrade adorned with statues of the Dioscuri, depicting Castor and Pollux alongside their horses, dating back to the Imperial era. The famous equestrian statue of Marcus Aurelius, for which Michelangelo created the podium, was placed in the center of the trapezoidal square in 1537. The original bronze statue of Marcus Aurelius, a copy of which can be seen in the center of the square, is preserved in the Capitoline Museums.

The Palazzo Senatorio, at the center of the square and home to the city's town hall, is a magnificent example of Roman architecture. Starting in 1144, it was affected by Michelangelo's intervention, who around 1546 created the façade with a frontal staircase with two flights that frame the fountain of the Goddess Roma, later created by Matteo Bartolani da Castello in 1588 at the behest of Pope Sixtus V. On the sides of the square, on the left is the Palazzo Nuovo and on the right the Palazzo dei Conservatori, both exhibition spaces of the Capitoline Museums.

The Palazzo Senatorio and the Palazzo dei Conservatori were completed after Michelangelo's death by Giacomo Della Porta, while the Palazzo Nuovo was completed by Girolamo Rainaldi and his son Carlo. The work was completed in 1655.
At the top of the building is the Torre della Patarina, built between 1578 and 1582 based on a design by Martino Longhi the Elder to replace the previous medieval tower. The epithet derives from the patarina, the name given to a bell brought from Viterbo as spoils of war by the Romans against the people of Viterbo in 1200. The current bell dates back to the 19th century but continues to be called the patarina and is rung on the occasion of the Birth of Rome, April 21st, and the election of the mayor.