8 Best Sights in Puglia, Basilicata, and Calabria, Italy

Crowning an isolated hill 1,778 feet above sea level in the heart of the Alta Murgia National Park, this enigmatic octagonal fortress, built by Frederick II in the first half of the 13th century, has puzzled historians and researchers for centuries. Rooms are arranged in a seemingly illogical sequence through eight towers around a central courtyard. Recent interpretations suggest it was an elaborate cultural center conceived by Frederick to study various scientific disciplines of the Western and the Arabic worlds. Umberto Eco used it as his inspiration for riddles in The Name of the Rose.

The massive Aragonese Castle is considered a masterpiece of 16th-century military architecture. Rebuilt by the Spanish viceroy Don Pedro di Toledo in 1535 after it was badly damaged in the siege of Otranto (1480), when invading Ottoman armies destroyed the city, its impressive walls and bastions dominate the port and seashore. Escape the heat with a walk around its cool interiors and more fascinating cellars (underground tours available for extra €4) that snake around its recently landscaped moats. Various art and photographic exhibitions are held here in the summer, although it lacks engaging interpretation materials.

The massive bulk of Gallipoli's castle guards the entrance to the island of the borgo antico, which is linked to the new town by a bridge. Rising out of the sea, the present fortress, dating from the 17th to 18th century, is built on the foundations of an earlier Byzantine citadel. It has four towers, plus a separate fifth known as the Rivellino, where open-air shows are held in summer. A visit allows grandstand sea views, but there's little to see inside between exhibitions.

Looming over the cathedral is the symbol of Bari: huge Castello Svevo, which houses a number of archaeological and art collections within its evocative courtyards, towers, and rooms. The current building dates from the time of Holy Roman Emperor Frederick II (1194–1250), who rebuilt an existing Norman-Byzantine castle to his own exacting specifications. Designed more for power than beauty, it looks out beyond the cathedral to the small Porto Vecchio (Old Port). Inside are displays that include plaster-cast reproductions of the city's sculptural riches, Byzantine archaeological finds, photo collections from Bari's past, and historic ceramics and other precious objects.

One of Frederick II's most imposing fortresses, the quadrangular Trani Castle guarded the Adriatic sea route throughout the Middle Ages. It was the scene of several royal weddings of the Swabian and Anjou houses, as well as the place of imprisonment for life of Siffridina, Countess of Caserta, who had supported the losing Swabian dynasty against Charles I of Anjou. In the early 20th century it became a state prison and remained so until 1974. The ground floor contains a museum telling the story of the castle alongside archaeological finds, sculpture, and a wealth of ceramics.

Originally built by Frederick II, this impressive structure was enlarged by the Spanish to defend against attacks from the Turks, and it has remained a military base ever since. It is only open to the public for guided visits and temporary exhibitions and events; call ahead for the latest information.

Castello Normanno Svevo crowns Pancrazio Hill above the old city, and the uphill walk rewards with wonderful views across to the Sila Mountains. Its origins are lost to memory: it may have been built by the Byzantines or the Saracens, and, before he was ousted by Normans, it was the residence of the Arab caliph Saati Cayti. What is known is that the castle takes its name from the great Swabian emperor Frederick II (1194–1250), who added two octagonal towers. Although extensively restored and open to the public, with audio guide/tablet tours (€1–€2) and occasional cultural events, the castle shows the ravages of successive earthquakes and a lightning strike that ignited gunpowder once stored within.