[18] Comparable remnants were discovered in an open-air site in São Pedro de Canaferrim, alongside the chapel of the Castelo dos Mouros (Moorish Castle), dating back to the Neolithic, and include decorated ceramics and microlithic flint utensils from the 5th millennium BC.

The most famous object from this period is the so-called Sintra Collar, a middle Bronze Age gold neck-ring found near the city at the end of the 19th century, which since 1900 has been part of the British Museum's collection.

Relatively close by, in Santa Eufémia da Serra, is an Iron Age settlement where artifacts from indigenous tribes and peoples of Mediterranean origins (principally from the Punic period) were also discovered.

[18] Close proximity to a large commercial centre (Olisipo) founded by the Turduli Oppidani people in the first half of the first millennium B.C., meant that the region of Sintra was influenced by human settlement throughout various epochs, cultures that have left remains in the area to this day.

A description by the geographer Al-Bacr, described Sintra as "one of the towns that [are] dependent on Lisbon in Al-Andalus, in proximity to the sea", characterizing it as "permanently submersed in a fog that never dissipates".

[18] This was preceded a year before by an attempt by Prince Sigurd the Crusader, son of Magnus III of Norway, to capture the castle from the Moors in the course of his trek to the Holy Land.

This community was not limited to Sintra town: enclaves are mentioned during the reign of King Denis in Colares, but were heavily pressured by the influx of Christian serfs.

[18] Many of Afonso Henriques' donations in the 12th century, including privileges assigned to these institutions, were confirmed in 1189 by his son, Sancho I (1185–1211), corresponding to a social, political and economic strategy during the post-Reconquista era.

[18] As Sintra was located relatively close to Lisbon, many of its people were called to work on projects for the Crown in the capital: in 1373, King Ferdinand decided to wall the city, and requested funds or workers from coastal lands in Almada, Sesimbra, Palmela, Setúbal, Coina, Benavente and Samora Correia, as well as all of Ribatejo, and from the inland areas of Sintra, Cascais, Torres Vedras, Alenquer, Arruda, Atouguia, Lourinhã, Telheiros and Mafra.

After the defeat of the Castilian army at Aljubarrota (August 1385) by Portuguese and English troops, commanded by Nuno Álvares Pereira, Sintra became one of the last places to surrender to the Master of Aviz, later King of Portugal (after 1383).

In 1545, the hospital was transferred to the administration of the Santa Casa da Misericórdia of Sintra which was set up by Queen Catherine of Austria, wife of John III.

King Manuel I (1495–1521) enjoyed spending his summers in Sintra, due to its cool climate and abundance of game; as Damião de Góis, his chronicler noted: "because it is one of the places in Europe that is cooler, and cheerful for whichever King, Prince or Master to pass their time, because, in addition to its good airs, that cross its mountains, called by the older peoples the promontory of the moon, there is here much hunting of deer and other animals, and overall many and many good trout of many type, and in which in all of Hispania there can be found, and many springs of water...".

These included the reconstruction of the old Gothic Church of São Martinho and in 1511 the construction of the Monastery of Nossa Senhora da Pena on the highest peak of the Sintra Mountains, which he then transferred to the Order of Saint Jerome.

The Renaissance poet Luisa Sigea—Syntrae Aloisiae Sygeae in Paris (1566) and Madrid (1781) referred to Sintra as a "pleasant valley, between cliffs that rise into the heavens...curved in graceful hills among which one can feel the murmur of the waters...[where] everything, in fact, will enchant and perfume the environment with its fragrance and fruit.

[18] In 1585 Mateus Alvares, born on the island of Terceira in the Azores and guardian of the hermitage of São Julio, passed himself off as King Sebastian and created conflict in Sintra, Madra, Rio de Mouro and Ericeira.

In 1838 the King-Consort, Ferdinand II bought the Monastery of Nossa Senhora da Pena and a vast adjacent area, commissioning the architect José de Costa e Silva to construct an arch joining the two quarters of the Seteais Palace (owned by the Marquis of Marialva), to commemorate the 1802 visit of the Prince and Princess of Brazil, John and Carlota Joaquina, and the subsequent visit of their son, the absolutist King Miguel, in 1830.

[18] The Palace of Pena, Sintra's exemplary Portuguese Romantic symbol, was initiated by the King-Consort Ferdinand, husband of Queen Maria II (1834–1853), a German-born member of the House of Saxe-Cobourg-Gotha.

Now a commission was established to monitor the quality of wines and promote their exportation, and in 1914 a commercial association (Portuguese: Associação Comercial e Industrial de Sintra) was set up to manage their concession.

Meanwhile, in the name of secular and popular progress, parts of the cultural heritage were destroyed, including the annexes of the medieval village bordering the palace in 1911, while the nave of the Church of the Misericórdia was reduced to the presbytery to allow the road to be widened.

[18] Archaeological studies resulted in considerable development: in 1927, Félix Alves Pereira rediscovered the Neolithic settlements of Santa Eufémia, and the first publication of the discoveries at the prehistoric monuments of Praia das Maçãs were completed in 1929.

[18] Many important Portuguese architects developed projects in the area in the first half of the 20th century, including Raul Lino, Norte Júnior and Tertuliano de Lacerda Marques.

These projects benefited town and region, increased tourism and attracted as residents many notable Portuguese: historian Francisco Costa; writer Ferreira de Castro; sculptor Anjos Teixeira; architects Norte Júnior and Raul Lino; painters Eduardo Viana, Mily Possoz and Vieira da Silva; poet Oliva Guerra; composer and maestro Frederico de Freitas; historians Felix Alves Pereira and João Martins da Silva Marques.

[21] The 1949 municipal plan by De Groer was devised to protect the town and its neighbourhood from uncontrolled urbanization, and resulted in the maintenance of an environment comparable to 19th century Sintra.

[18] The Sintra Mountains, a granite massif ten kilometres long – considered the Monte da Lua (Mountain of the Moon), or Promontorium Lunae by the strong local tradition of astral cults – emerge abruptly between a vast plain to the north and the northern margin of the Tagus River estuary, winding in a serpentine cordillera towards the Atlantic Ocean and Cabo da Roca, the most westerly point of continental Europe.

[23] The Eruptive Massif of Sintra (MES) is a dome structure, formed by layers of sedimentary rocks (limestones and sandstones) from the Upper Jurassic and early Cretaceous periods.

[23] A metamorphosed igneous intrusion resulted in a narrow halo of metamorphic rocks, but also strongly deformed these sedimentary layers causing a vertical exposure.

[23] The geodynamic conditions that controlled the formation of the MES (correlated with the development of the Sines and Monchique Eruptive Massifs) are associated with the progressive northern expansion of the Atlantic Ocean and the consequent opening of the Bay of Biscay.

[22][24] For different reasons (the climate here has been moderated by the Sintra Mountains; the fertility of the soils; and its relative proximity to the Tagus estuary) the region attracted considerable early settlement.

The temperate climate and humidity resulting from proximity to the coast favour the growth of a rich mat of forest including Atlantic and Mediterranean species, marking the transition in Portugal from northern to southern vegetation.

Other species scattered throughout the mountains of Sintra include: maple (Acer pseudoplatanus), common hazel (Corylus avellana), common hawthorn (Crataegus monogyna), European holly (Ilex aquifolium), Portuguese laurel (Prunus lusitanica), Bay laurel (Laurus nobilis), strawberry tree (Arbutus unedo), laurestine (Viburnum tinus), Kermes oak (Quercus coccifera), and Italian buckthorn (Rhamnus alaternus).