The Olèrdola Monumental Complex is located on a rocky platform 358 m high, on the western slopes of the Garraf massif, within the Olèrdola Park, overlooking the Penedès plain.
The first known fortification is from the Iberian period (9th-8th century BC). This defensive wall is parallel to the well-known Roman-Republican wall and preserves an internal transverse wall, the upper part of which was used in the Iberian period. During the 4th century and until the end of the 2nd century BC, an occupation by an Iberian town is documented. In this Iberian phase, the Late Bronze wall is reused and there is an adaptation of houses and a street, structured with respect to the defensive wall of the wall and which would be included in the later tower of the Roman-Republican era.
At the end of the second century BC, the Romans built another wall in front of the previous one, a watchtower and probably a large cistern carved into the rock with a capacity of more than 350 m3. The cistern measures 16.40 m long x 6.50 m wide x 3.5-4 m deep. This cistern is considered to be from the Iberian or Roman-Republican period and was reused in the medieval period. 2 quarries were also located from this period (end of the 2nd century - beginning of the 1st century BC), one inside the walled enclosure and the other in front of the wall. Towards the middle of the 1st century BC, Olèrdola was abandoned but there was a medieval occupation from the 9th century. It seems that a field of silos cut into the sediment belong to an early period of medieval occupation.
Within the medieval fortified enclosure, the space was structured in three areas. At the top was the military area, with the castle at the top and, further down, the sacred area, with the church and the necropolis. The lower part of the mountain was occupied by houses.
In 1963 the Diputació de Barcelona acquired the property. In November 1971, after some renovations to the church and the construction of a new building on the site occupied by an old farmhouse-rectorship, the monumental complex of Olèrdola was opened to the public. Since 1995 the historical complex of Olèrdola has been one of the headquarters of the Museum of Archeology of Catalonia. Olèrdola was declared a Cultural Property of National Interest in 1931 and a Property of Cultural Interest (BIC).