The site was likely the location of fortified settlement during prehistory. Legend suggests that during the 2nd century a
castro was taken and colonized on the hilltop of Mons Sanctus, by
Roman Praetor Lucius Aemilius Paullus. The castro was destroyed and progressively settled by settlers from Idanha-a-Velha. Between the 5th and 11th century was occupied by Visigoths and Arabs. In order to build a defensive line and strengthen his presence in the region, D.
Afonso I of Portugal donated the area to D.
Gualdim Pais, Master of the
Templars; a vast region, that extended to the territory of Egitânea (corresponding to
Idanha-a-Velha) along the
Rio Erges. :''"Afonso, remarkable king of the Portuguese" (Portugalensium rex)", son of
Henry and Queen D.
Teresa and grandson of the great and illustrious Emperor of Hispania, for us to master Galdino and all the brothers of the Knights Templar who are in my kingdom, I make a wide and giving very strong in the region of Idanha [-a-Velha] and Monsanto with the limits: Following the course of the river and between Erges my kingdom and the 'legions' to enter the [river]
Tagus and the other party following the course of water [river]
Zêzere River which also enters the river Tagus (...). ''" (Letter of Donation on 30 November 1165.) The castles of Monsanto and Idanha-a-Velha were constructed by 1171, when a
foral (
charter) was donated to the settlement, following the model of Ávila/Évora. During the course of litigation with the
Order of the Temple in 1172, the castle was donated to the
Order of Santiago ("
facio cartam donationis de castello meo proprio quad dicitur Mons Sanctus"), with the condition of not nominating an unknown commander. As a result of this change, in 1174, a new foral was issued to the inhabitants of Monsanto, by D. Afonso Henriques, which was confirmed in 1190 by D.
Sancho I. A contemporary castle was constructed during the 13th century. It was reconstructed in the 14th century, during the reigns of King D.
Dinis and D.
Fernando. But, following its alignment with the Kingdom of Castile during the
1383–1385 Portuguese interregnum, the site began to fall into disorder. According to the chronicler
Fernão Lopes, Monsanto was a village that had been loyal to
Queen Beatrice. But, later however, Lopes listed the town among those aligned themselves with D.
John by 1384. Beginning in the 1476, the area was reconstructed during the reign of King D.
John I, resulting in the construction of a barbican and protection over the well, a large chamber that belonged to the Castro family (later identified as providing abundant water for the site). By 1496, the
Inquirição indicated 309 inhabitants. by Duarte d'Armas showing the castle on the clifftops At the beginning of the 16th century, Duarte de Armas conducted a graphic survey for his
Book of Fortresses, designing the castle with two access gates (the oldest opened to the cliffs) and protected by two towers. In total there were four towers, a keep and cistern. The
Torre do Pião (lookout tower) was in ruins at that time. Supported by an alcaide, the urban nucleus included the parish of São Miguel and the parish of São Salvador. In the late 16th century, there was work performed during the reign of King D.
Manuel I. By 1527, during the
Numeramento (medieval census) there were 494 inhabitants. In the second half of the 17th century, the structures were adapted to support artillery, with the construction of earthenworks, batteries and canon emplacements, as well as fortification walls for the colony. This followed the 1704 siege by Franco-Spanish forces, under the command of the
Duke of Berwick, but later liberated by the
Marquess of Minas. By 1758, surveys of the site indicated one of the towers in ruin. Reconstruction of the fortification walls were undertaken by order of
William, Count of Schaumburg-Lippe following the
Spanish invasion of Portugal. Similar alterations were built in 1801, a slope was established in order to implant canons. Major Eusébio Furtado was later responsible for the installation military garrison in 1813, resulting in major works on the castle. But, in 1815, there was an explosion of the magazine powder keg, resulting in the partial destruction of the castle. Surveys were undertaken by military engineer Maximiano José da Serra following the disaster, and military descriptions for the site were written in 1823, by Eusébio Cândido Cordeiro Pinheiro Furtado. An 1831 collapse of a cliff resulted in the destruction of an exterior wall and a time when the Chapel of Santa Maria was in a state of ruin. Meanwhile, the Church of São Miguel continued to be open to the cult as late as 1834. In 1853, the municipality of Monsanto was extinguished, leaving its second-order military status and militia. The 12th Infantry Regiment was stationed to the square of Monsanto in 1887. The first work on repairing or conserving the site began in 1940, when the DGEMN
Direção-Geral de Edifícios e Monumentos Nacionais (
Directorate-General of Buildings and National Monuments) began restoration of the walls, detailed excavations on site and removal of topsoil. In the following two years, the work continued with consolidation of the walls and granite, construction and placement of masonry. Between 1957 and 1958, further work began that included further repairs to the walls, reconstruction of the towers and reinforcement of the ashlar stones. In 1986, complementary work continued in the castle area that included repairing loose ashlars and consolidation of the pavement along the adarve in the west. Between 1988 and 1989, there was work on consolidating the walls and pavements, the adarve and accessways to the castle. Much of the archaeological artefacts extracted from Monsanto were dispersed throughout various museums, among which were the Museum Francisco Tavares Proença Júnior in Castelo Branco. ==Architecture==