Alghero developed on Sardinia's northwestern coast around a fortified medieval settlement associated with the Doria family of Genoa. Its harbor faced trade routes linking Sardinia, Liguria, Iberia, and North Africa, while walls and towers protected merchants, fishers, soldiers, artisans, and warehouses. The precise sequence of early foundation is debated, but by the twelfth and thirteenth centuries Alghero functioned as a strategic maritime town within the rivalries of Genoa, Pisa, local Sardinian powers, and the expanding Crown of Aragon.

Aragonese forces captured Alghero decisively in 1354 after revolt and renewed warfare. Many earlier inhabitants were expelled, and settlers from Catalonia and other Crown of Aragon territories repopulated the town. Catalan became embedded in civic, commercial, and family life and remains a distinctive element of Alghero's identity. Churches, houses, lanes, quays, and defensive works were rebuilt within a tightly enclosed urban plan. The town served royal administration and helped secure Aragonese control over Sardinia.

Spanish rule brought repeated changes to the fortifications as artillery altered siege warfare. Rounded towers, bastions, sea walls, gates, and gun positions strengthened the harbor and landward approaches. Alghero endured epidemic disease, economic fluctuation, and threats from rival fleets and corsairs, yet fishing, coral working, agriculture, and regional trade sustained it. Religious confraternities and merchant families endowed churches and chapels, while the cathedral and civic buildings expressed the authority of Crown, church, and municipal institutions.

Sardinia passed to the House of Savoy in the eighteenth century, and Alghero's military role gradually declined. Sections of the landward walls were removed or absorbed as the modern town expanded, while the seaward ramparts, towers, and historic center survived. Nineteenth- and twentieth-century roads, tourism, war, and new housing changed the setting. The old harbor became less a fortified frontier and more a gateway through which visitors encountered the city's architecture, cuisine, coral traditions, and Catalan language.

Alghero Old Town remains a living district rather than a sealed archaeological site. Residences, shops, churches, public buildings, restaurants, and visitor facilities occupy medieval and early modern streets whose fabric has been repeatedly repaired. Conservation must balance local housing and commerce with heavy tourism and exposure to salt, wind, and sea. The district's significance comes from cultural persistence: conquest altered its population in the fourteenth century, but the resulting Catalan-Sardinian identity survived later dynasties and gives the walls, language, and urban landscape a relationship found nowhere else in modern Italy today, especially along the western Mediterranean coast.