In fact, the builders of the first enclosures of Perdigões, in Late Neolithic, chose the lower centre of this topography, where visibility was restricted in every direction except to East, in an overture with limits coinciding with the two solstice annual events.
The topography selected responded to symbolic needs, not to defensive ones. That is obvious.
And it is also obvious that the general idea was present when the later ditches defined a larger enclosure, respecting the topographical limits of the amphitheatre and orientating the gates to the two solstices.
The topographical location of Perdigões and relation with the ditched structures is one of the strong arguments in favour of a cosmological foundation of the enclosures architecture through the long life of the site.