One of the Romans' top priorities was securing their new settlement, so they built a sturdy defensive wall around Barcino. The first wall stood 9 meters tall, complete with towers and four gates—one on each side of the city. In the 4th century AD, fearing barbarian invasions, the Romans reinforced the structure, raising its height and adding 76 defensive towers along the perimeter. Today, you can still spot sections of this ancient wall cleverly woven into medieval buildings—a striking fusion of eras and architectural traditions.