The Roman city was walled between the late 2nd and early 4th centuries AD. The area is oval to cater for the irregular terrain with a perimeter of around 750 m. The sturdy wall reused a lot of previous construction materials. It is reinforced with regularly spaced perimeter towers. The wall constricted the urban area and substantial parts of the town were left outside, including houses and some thermal baths. Later, during the Muslim occupation, the wall was restored and strengthened though they did not change its appearance much. The Knights Templar seem to have used the fortress like a fence, which was occasionally repaired. The North Gate into the city has three round arches all based on salient posts and it is bordered by two of the semi-circular turrets. The road to Braga started here.