Balaguer Castle has been known as Formós Castle since the late Middle Ages. The date of its foundation is known thanks to the historian Ibn Hayyan, who collects the story of Isa b. Ahmad al-Rasi, who places the construction of the Hisn Balagi - Balaguer Castle - in October 897 AD. At this point the castle is basically a fortification and serves as the residence of the governor, who holds local power. Its construction responds to the desire that it be a construction that can defend itself in the event of a siege.

In the middle of the 11th century, a palace was built inside, which was decorated with refined atauric figures made on plaster and which were polychrome. The decorative motifs are mainly vegetal and geometric, but there are also epigraphic friezes where fragments of the Qur'an are read; and zoomorphic motifs, such as a harpy with hands.

With the conquest of the beginning of the 12th century, the counts of Urgell occupied the old palace and made it their residence. In the 14th century, major renovation works were carried out that led to the conversion of the entire northern area into a large garden, irrigated by ceramic water channels, built with tiles and tiles made by Moorish artisans.

Balaguer Castle was destroyed in 1413 following the war between the last count of Urgell, Jaume II el Dissortat, and King Ferran I of Antequera.