Of Andalusian origin, the Suda Castle, also known as Castell del Rei, was the as-sudda or citadel of the city.

The remains of the Suda, now restored, are located on the hill of La Seu Vella, behind the old cathedral of Lérida. Its existence is documented from the year 882, when the city was occupied by the Saracens. It was built there because from this location it overlooked a vast territory, stretching from the Pyrenean massifs of Monte Perdido and Cotiella to the mountains of Prades and Montsant, including the entire plain of Lérida, and it was an excellent place of defence. Between 1031 and 1036 it served as a refuge for the dethroned Hisham III, the last Caliph of Córdoba.

From the time of the Christian conquest onwards, the castle of La Suda was the site of some remarkable historical events. In 1150, the marriage between the Count of Barcelona and prince of the Aragonese Ramón Berenguer IV and Petronila of Aragon, daughter of King Ramiro of Aragon, was celebrated here. This marriage confirmed the union of the Kingdom of Aragon with the Casal de Barcelona and the birth of the Crown of Aragon. In 1214, in this castle, the Catalan and Aragonese nobles swore allegiance to the infant James, who would become King James I "the Conqueror". At the height of its splendour, the castle of La Suda became the Lleida residence of the Counts of Barcelona.

It had a rectangular floor plan with the different rooms around a central courtyard, a porticoed belvedere on the north side and the royal chapel on the east side. King James I ordered the wooden coffered ceilings to be replaced by ribbed vaults. Only the southern sector, the closest to La Seu Vella, has survived. It has a façade articulated by three towers with loopholes and openings.

After the War of the Spanish Succession, the entire hill, the seat of the primitive city of Lérida, which had already acquired a strong military character during the "War of the Reapers", was converted into a military fort by order of Philip V. La Suda was used as a gunpowder magazine. The explosion of 1812, during the War of Independence, destroyed the royal chapel and the porticoed gallery on the north side. A second explosion during the Civil War in 1936 ruined the west façade, where the main entrance to the castle was located.

Today, a fifth of what was once the castle remains, basically ruins, the central well and the southern gallery or noble hall, a nave with Gothic ogives, which were dismantled at the beginning of the 20th century, and which now has a new wooden coffered ceiling. This southern nave or noble hall has recently been consolidated and refurbished, and an interpretation centre of the "Turó de la Seu Vella" will be installed there, which will be open to the public in mid-2010.