The establishment of Valletta as the capital city of Malta marked a significant transformation for the Maltese archipelago. Following the Great Siege of 1565, in which the Knights of St. John successfully defended Malta against the Ottoman Empire, the need arose to create a fortified city to bolster military and civilian power. Grand Master Jean de la Valette recognized that a strategically located, well-planned city would serve as a safeguard against future invasions while providing a centralized governance location for the Knights and local inhabitants.

Construction began in 1566 and was meticulously designed, incorporating elements of Renaissance and Baroque architecture. Valletta was planned by the Italian military architect Francesco Laparelli, and construction of its fortifications and key structures, including the Co-Cathedral of St. John and the Grandmaster's Palace, effectively transformed the urban landscape. The design of the city featured broad streets, public squares, and impressive fortifications, all built to withstand further sieges.

By 1571, the city had gained prominence and was officially designated as the capital of Malta, overshadowing Mdina, the ancient capital. This change not only reflected Valletta’s status as a military stronghold but established it as an administrative and cultural hub for the Knights of St. John. Over the years, Valletta flourished, attracting artists, architects, and craftsmen, thus enriching the cultural tapestry of the island. This legacy continues to be visible in the architecture and urban layout established during this pivotal period.