Although the first fortification on this hilltop date to the 2nd century BCE, archaeological excavations have identified a human presence in the Tagus valley as far back as the 6th century BC. The first fortification was, presumably, erected in 48 BCE, when Lisbon was classified as a Roman municipality.[1]
The hill was used by indigenous Celtic tribes, then by Phoenicians, Greeks, and Carthaginians, as a defensible outpost, that was later expropriated by Roman, Suebic, Visigothic, and Moorish peoples. During the 10th century, the fortifications were rebuilt by Muslim forces, that included the walls or Cerca Moura (Moorish Encirclment).