The oldest accounts of a roman sanctuary by the mouth of the river of Colares date back to the 16th century. Their authors are Valentim Fernandes, in 1505, and Francisco d’Ollanda, around 1541. The latter published in his book “Da Fábrica que falece à cidade de Lisboa” a drawing of the structures of the sanctuary that he reportedly saw.
The identification of these ruins such a long time ago was in fact the first archaeological discovery made as such in Portugal. The importance of the place was widely acknowledged back then, having it become an obligatory visit for Portuguese and foreign scholars during the Renaissance. Among the illustrious visitors were Francisco d’Ollanda and André de Resende, but also members of the Royal family, notably King Manuel I and, later, the Infant Dom Luís, brother of King João III.
The accounts of the visits to the site show that it remained an attraction during nearly the whole of the 16th century, after which the structures must have progressively become less visible, to the eventual point of their precise location being lost.
In spite of this, the memory of a roman sanctuary on the coast of the Sintra region remained, although its whereabouts had become unknown. Recent research ended up pinpointing a small hill next to Praia das Maçãs, where still today the designations Alto da Vigia (watchtower hill) and Alconchel are maintained.
It was exactly on that very same hilltop, on the left bank of the stream, that the team of the Archaeological Museum of São Miguel de Odrinhas began an intervention in 2008, next to the partially visible ruins of a watchtower.
This archaeological intervention confirmed the existence of a monumental roman sanctuary, and also that the watchtower dates back to the early 16th century. Surprisingly, an important Islamic settlement, whose existence was totally unknown, was equally found, being probably connected to the name Alconchel (al-concilium).
Its architecture reveals it was a ribat (convent), with several rooms uncovered so far, one of which includes a mirhab turned to the southeast, in the direction of Mecca.
The presence of Islamic material remains of daily utilization is very scarce. However, a few ceramic shards dating to the 12th century were found, and probably belong to the final stage of occupation. Many seashells were present, some still in connection with fireplaces, indicating the exploitation of local seafood.
Besides the walls, a necropolis with several graves was also identified. Despite the absence of any remains within, they were most likely contemporary with the Islamic occupation of the place.
Numerous stones in the walls of the ribat are reutilized Roman architectural elements, including some inscriptions, which corroborate the existence of an important Roman sanctuary, already hinted at in the written accounts of Valentim Fernandes and Francisco d’Ollanda.
The importance of the sanctuary is made evident from the fact that the inscriptions known so far, in honour of the health of the Emperor and the eternity of the Empire, are dedicated neither by regular citizens, nor even local or provincial elites, but only by holders of high imperial positions, notably governors of Lusitania or legates of the Emperor, although sometimes through the senate of Olisipo, municipality whose territory included this particular area.
During the excavations, a new inscription was recovered that further demonstrates the significance of the place, being dedicated to the Sun and the Ocean by a Procurator of the August Emperors and his family. Besides this altar and a funerary inscription dating back to Augustus – older than the sanctuary itself – other masonry pieces were found, some monumental, such as a decorated capstone, fragments of columns and altars, and large building blocks.
The Islamic structures are in many places very damaged due to the removal of large blocks, some of which having left placement marks on the mortar of the foundations they belonged to, or the smaller support stones used to level them inside the ditches. However, some of those large blocks, a few finely crafted, are still extant in the walls. Probably the removal of stones is connected to the building of the watchtower in the early 16th century, when the Islamic structures must have been partially utilized as a quarry.