Short answers, pulled from the story.
The Capitoline Hill was originally known as Mons Saturnius before workers found a human skull during temple construction. The Latin word caput means head, and this discovery defined the hill's new name according to Varro L.L. 5.7.42.
The Capitoline Hill remained the only section of Rome to evade capture by the Senones Gauls after the battle of River Allia. Roman defenders fortified the slopes while sacred geese of Juno alerted guards to climbing enemy forces led by Marcus Manlius Capitolinus.
Construction began under Tarquinius Priscus who ruled from 616 to 579 BC and finished between 535 and 496 BC under King Tarquinius Superbus. The temple stood nearly as large as the Parthenon when completed in 509 BC.
Renaissance artist Michelangelo Buonarroti created the design for Piazza del Campidoglio between 1536 and 1546 at the commission of Pope Paul III. Work continued after his death under Tommaso dei Cavalieri's supervision until the Campidoglio was completed in the 17th century.
Three palazzi now house the Capitoline Museums including the Palazzo dei Conservatori, the Palazzo Nuovo, and the Palazzo Senatorio. The Palazzo dei Conservatori stands atop a sixth-century BC temple dedicated to Jupiter Maximus Capitolinus while the Palazzo Senatorio houses Roman city hall.