There is no certainty whether it was the Ponta de Sagres, whose name came from Sacrum Promontorium, or the nearby Cape St Vincent, that was thought to be sacred promontory. Estrabo(was a historian, geographer and Greek philosopher) believed that the promontory was the westernmost point of “all the inhabited world”.
In fact, the Cape St. Vincent is further west, but to be further north, the Strabo map of the Iberian Peninsula is rotated in a clockwise direction, leaving the Pyrenees in a north-south line, and may have been taken as being more west. The westernmost point of the Iberian Peninsula and continental Europe is the Cabo da Roca, west of Sintra; the southernmost is the Punta de Tarifa, Andalusia.
Strabo says Artemidorus mentions three islands to protect docking sites that point. No part of Cape St Vincent matches this description, but on the eastern side of Ponta de Sagres there is a port (now the modern port of Sagres) with ancient structures protected by four small islets in a row (already in Cove Martinhal, so-called islets Martinhal). Strabo had stated that ship shape.
Strabo also states that Artemidorus reported that there were no temples in the sacred promontory, only stones. According to the customs, swinging stones should be rotated by visitors, one poured libation, and rotated stones to their original positions. The sacrifices were not allowed, nor the overnight stay in place, asserting that it was when the gods came. There was no water, and had to be brought by visitors.