Spectacularly transformed by Michelangelo's late-Renaissance designs, the Campidoglio was once the epicenter of the Roman Empire, the place where the city's first shrines stood, including its most sacred, the Temple of Jupiter. The Capitoline Hill originally consisted of two peaks: the Capitolium and the Arx (where Santa Maria in Aracoeli now stands). The hollow between them was known as the Asylum. Here, prospective settlers once came to seek the protection of Romulus, legendary first king of Rome—hence the term "asylum." Later, during the Republic, in 78 BC, the Tabularium, or Hall of Records, was erected here.
By the Middle Ages, however, the Capitoline had become an unkempt hill strewn with ancient rubble. In preparation for the impending visit of Charles V in 1536, triumphant after the empire's victory over the Moors, his host, Pope Paul III Farnese, decided that the Holy Roman Emperor should follow the route of the emperors, finishing triumphantly at the Campidoglio.
The pope was embarrassed by the decrepit goat pasture the hill had become and so commissioned Michelangelo to restore the site to glory. The resulting design added a third palace along with Renaissance-style facades and a grand paved piazza. Newly excavated ancient sculptures, designed to impress the visiting emperor, were installed in the palaces, and the piazza was ornamented with the giant stone figures of the Discouri and the ancient Roman equestrian statue of Emperor Marcus Aurelius (the original now housed in the Musei Capitolini)—the latter suggesting a parallel between the glory of Charles V and that of the ancient emperor.
The piazza centerpiece is the legendary equestrian statue of Emperor Marcus Aurelius, but in 1999 a copy replaced the 2nd-century-AD original, which moved to a new wing of the surrounding Musei Capitolini. The Sala Marco Aurelio and its glass room also protect a gold-plated Hercules along with more massive body parts, this time bronze, of what might be Constantine or that of his son Constans II (archaeologists are yet undecided). While there are great views of the Roman Forum from the terrace balconies to either side of the Palazzo Senatorio, the best view may be from the Tabularium, the arcade balcony below the Senatorio building, accessible with admission to the Musei Capitolini. The museum also has the Terrazza Caffarelli, featuring a restaurant with a magical view toward Trastevere and St. Peter's.