The architectural structures found on the Royal Mountain — today known as Colle San Vitale — date back to the Middle Ages, roughly between the 7th and 16th centuries. However, the site had already been inhabited for many centuries before that. Archaeologists have discovered ceramic fragments from various periods: the most numerous date to the 4th–2nd centuries BCE, but there are also older finds, including black-glazed pottery from the 7th–6th centuries BCE.

Among the most important discoveries is an archaic tetradrachm from Syracuse. This finding has led some scholars to suggest that the hill may have hosted a military outpost from Agrigento, possibly connected to the colonization route launched in the 5th century BCE by Phalaris from Agrigento to Himera.

After the destruction of the earlier settlement in 848 CE at the hands of Arab forces, the history of Castronovo shifted to this very mountain. It was here that the Arab ruler Abdu Beker ordered the construction of the Emir’s Castle. The Arab elites made the castle their residence, while the hill also remained home to a learned clergy and local nobles of Greek and Byzantine heritage.

The lower slopes of the mountain became home to the Arab working classes, who established the neighborhoods of Rabat and Rakal-Biat.

In 1077, Arab rule came to an end with the arrival of Count Roger of Hauteville, who expanded and fortified the castle. Due to the current state of decay, it is difficult today to determine the exact age of the castle or to trace later structural changes.

The medieval settlement developed along a grid-like plan centered around a main road aligned with the castle. The surrounding walls were built from irregularly shaped limestone blocks, reinforced with tile fragments and bound with mortar. Their layout followed the uneven contours of the terrain, with variable thickness.

Within these walls, visitors can still see the remains of a cylindrical tower and a rectangular cistern, partly dug into the rock and covered with a vaulted ceiling. Several carved holes in the stone indicate the former presence of a drawbridge that once entirely isolated the hilltop.

At the summit, the ruins of the castle still stand, and in precarious condition, the Church of the Righteous Judge, featuring three apses decorated with Byzantine-style frescoes.

In 1302, King Frederick III of Aragon chose the castle as his military headquarters. From here, negotiations began that led to the famous Peace of Castronovo — also known as the Peace of Caltabellotta.

From the 14th century onward, however, the Royal Mountain was gradually abandoned.

Residents began relocating to the current town site, which offered a more sheltered and accessible setting.

Today, visitors to the hill can still explore the Church of Saint Vitalis, patron saint of Castronovo; the Church of the Hearing, once the main church of the Greek-Byzantine rite; the ruins of the Church of Saint Mary of the Miracles; and the hospice of the Teutonic Knights.