Though the word castle has been applied to some prehistoric structures, the evolution of what we know today as the archetypal castle began accelerating in the 9th century in Europe. But some came much earlier, including one in this list. Here are six of the most notable castles in Italy.

　　Earlier versions of the descriptions of these castles first appeared in 1001 Amazing Places You Must See Before You Die, edited by Richard Cavendish (2016). Writers’ names appear in parentheses.

　　The Castel Nuovo (New Castle), so named to differentiate it from the old one, Castel dell’Ovo (Egg Castle), was built on orders from Charles of Anjou after he became king of Sicily in 1266. Before 1266, Palermo was the capital of the kingdom, but Charles moved his base of control to the city of Naples and in 1279 commissioned a mighty fortress to be built there, near the sea. It was completed by 1282, but the bloody events of the Sicilian Vespers in that year—a riot and massacre in Palermo that triggered a widespread Sicilian rebellion against Charles—prevented the royal family from moving into the palace until after Charles’s death in 1285.

　　The poets Petrarch and Boccaccio were both invited to the court here during King Robert’s brilliant reign in the 14th century, and Giotto created frescoes (now lost) on the building’s walls. The castle was greatly enlarged and embellished under Robert, who was a great patron of the arts. The magnificently carved arch over the west entrance chronicles King Alfonso V of Aragon’s triumphal march into Naples in 1443. The bas-reliefs are credited to Francesco Laurana, one of the most important and complex sculptors of the 15th century. On a different note, in 1485 Alfonso’s son Ferdinand I invited a group of barons who were plotting against him to a feast in the Sala dei Baroni. Some accounts say the doors were locked and the barons arrested, then executed. A more colorful version claims that Ferdinand had boiling oil poured over them from the ceiling. The city council of Naples met regularly in this room until the early 21st century.

　　In 1494 the kingdom of Naples was annexed by Spain, and the castle was demoted from residence to military fortress. Today it contains important artwork, sculpture, and frescoes from the 14th and 15th centuries, as well as the city’s Museo Civico, which displays mostly local artwork from the 15th to the 20th century. (Robin Elam Musumeci)

　　Castel Sant’Angelo (Rome)Built between 135 and 139 CE, Rome’s Castel Sant’Angelo was commissioned as a mausoleum for the ashes of the Roman emperor Hadrian and his family. Later emperors followed suit, and the last emperor laid to rest there was Caracalla, who died in 217. By the 5th century the building had been converted into a military fortress, and further fortifications were added over the next thousand years to make it a papal fortress. The castle has also been used at various points in its history as a prison, housing heretics such as the 16th-century philosopher Giordano Bruno and the 18th-century adventurer and scandal-sower Alessandro, conte di Cagliostro.

　　Castel Sant’Angelo received its name from Pope Gregory the Great in 590, after he had a vision of the archangel St. Michael’s appearance above the building, symbolically marking the end of a plague in the city. In 1536, to mark this event, a marble statue of St. Michael by Raffaello da Montelupo was erected on top of the castle. In 1753 this was replaced by a bronze statue by the Flemish sculptor Peter Anton von Verschaffelt. Montelupo’s statue was later moved to an interior courtyard in the castle.

　　In 1277 a wall and a 2,625-foot- (800-meter-) long secret passageway—the Passetto di Borgo—were built by Pope Nicholas III to connect the fortress to Vatican City and enable popes to escape to safety when under threat. The passage was used in 1494 by Pope Alexander VI when King Charles VIII of France invaded Rome and again in 1527 when hundreds of people, including Pope Clement VII, took refuge in the fortress for months during an attack on Rome by the Holy Roman emperor Charles V. Clement’s successor, Pope Paul III, built lavish apartments in the castle for the use of any future pope taking refuge there. (Carol King)

　　Castello di San Michele (Ferrara)In 1264 the Guelf family of Este, in a war of dominance for the city of Ferrara, overcame the rival Salinguerra family and finally became lords of the city and its territory—although they would never be accepted or beloved by their subjects. Matters came to a head when the people of Ferrara, worn out by famine and exasperated by endless taxation, rose up against the Estensi in a bloody rebellion in 1385. Though the rebels were overcome, the event put such fear into Nicolò II d’Este that he commissioned a fortress, the great Castello di San Michele (also known as Castello Estense), to be built around an existing watchtower, the Rocca dei Leoni (Lion’s Fortress), in the northern city wall to protect him and his family.

　　This mighty fortress became the symbol of a despotic and absolute power over a subdued city, an indication of the wealth and political and military control of the Estensi. It was not until 1476, however, after Ercole d’Este defeated a bloody bid for power by his nephew, that the family took up full residence within the castle’s environs and work began to improve and expand their apartments. In 1598 Alfonso II d’Este, who had already been married three times, faced the fact that he had no legitimate male heir or even a successor who would be recognized by the church. He made various attempts to prevent the end of the house of Este and its property’s expected annexation by the church, but the family was finally forced to abandon Ferrara, and the castle was taken over by the Papal States, becoming the home of the Cardinal Legates.

　　Almost 300 years later, the Provincial Administration of Ferrara purchased the fortress at auction and established its offices there. The rest of the castle was restored and opened to the public. (Robin Elam Musumeci)

　　The Castello di Sarre is a castle located in Sarre, a small town in the Aosta Valley, in northwest Italy (hence the name by which it is known). From the 11th century the Aosta Valley was ruled by the house of Savoy, which later became the Italian royal family. In the 19th century the Castello di Sarre became the hunting lodge of Victor Emmanuel II of Savoy, the first king of a united Italy. The Castello di Sarre is located on a hill overlooking the Aosta Valley. Its origins are obscure, but its foundations may date as far back as the 11th century. The castle passed through the hands of various local aristocrats until in 1708 it was purchased by Baron Jean-François Ferrod. He completely rebuilt the castle, leaving only the tower in place from the original structure.

　　Victor Emmanuel II purchased the castle in 1869. A keen hunter, the king extended the tower so it could be used as an observatory and added stables. His son, who became King Umberto I, also used Sarre as a hunting lodge and added extensions in 1900. The last king of Italy, Umberto II, was a frequent visitor until his exile in 1946.

　　Despite the king’s exile, the Castello di Sarre remained the property of the house of Savoy until 1972. Today it is owned by the local government and houses a museum. (Jacob Field)

　　Castello Sforzesco (Milan)The enormous Castello Sforzesco is situated to the northeast of Milan’s famous crenellated Duomo. It began life as a defensive fortress, owned by the ruling Visconti family, built across the city’s medieval walls. The castle was an integral part of the city’s fortifications, growing in size as each successive Visconti added on to it, until the last Visconti, Filippo Maria, turned it into a residence and lived there until his death in 1447.

　　The Milanese people had had enough of Visconti tyranny, so after Filippo Maria’s death they established the Ambrosian Republic and took up any weapon they could find to tear down the walls of the castle. The stones were then used to pay off debts and rebuild the city walls.

　　Filippo Maria had an only daughter, Bianca Maria, who was illegitimate but was recognized as his heir. She had married Francesco Sforza—a mercenary who had been recruited to defend the dukedom of Milan from its Venetian neighbors. In the three years after Filippo Maria’s death, Sforza, a political opportunist, defended the city and the republic against its greedy neighbors. He then used the situation to his advantage and took power in March of 1450, supported by his wife. He began to rebuild the castle with the idea of making it a symbol of Milan’s beauty and power, employing military engineers and the Florentine architect Filarete.

　　At the end of the 15th century, however, the castle went into a long decline. It was left to fall into partial ruin before being restored to house the city’s art collection in the late 1800s. Today visitors to the museum can marvel at ceiling frescoes by Leonardo da Vinci, paintings by Fra Filippo Lippi, and a vast collection of Egyptian and prehistoric artifacts—as well as the moving and beautifully unfinished Pietà Rondanni by Michelangelo. (Robin Elam Musumeci)

　　Castelvecchio (Verona)Romeo and Juliet’s world-famous city of Verona is known not only for its romantic balcony but also for other remarkable monuments, of which Castelvecchio is one of the most emblematic. Originally it was named St. Martin’s, after the old church that was included within its walls in the Middle Ages, but its name was changed to Castelvecchio (Old Castle) when a new manor was erected in the 14th century.

　　Castelvecchio, on the banks of the Adige River, was the fortress of the della Scala (Scaliger) family, which ruled Verona until 1387. It was built by Cangrande II della Scala in 1354, during a period of turbulent events. Its military aspect is stately, and massive towers surround the big parade ground and the main tower. In case of an assault, the family’s escape route was assured northward, by way of the Ponte Scaligero. Like the castle, this bridge was constructed in red brick and white marble, and it was fortified with walls and towers.

　　When Verona fell under Venetian control in 1404, the castle was used as an arms store; by the 18th century it was the seat of the military academy of the Venetian republic. In 1923 the building lost its defensive function and was restored and converted into a museum. The castle hosted a historic trial in 1944 that sentenced to death the generals who had voted to remove Mussolini from office. It was, however, the restoration conducted in 1957 by the architect Carlo Scarpa that turned the museum into a masterpiece of Italian museography, with famous works from the early Christian era through the 18th century. The ensuing archeological excavations brought to light ancient structures and unveiled a forgotten history.

　　Today Castelvecchio, with its powerful medieval architecture and impressive bridge, is one of the most spectacular tourist attractions in Verona. (Monica Corteletti)