The aim of this thesis is to investigate ideas of empire and imperialism in the architecture, urbanism and culture of the Iberian Peninsula during the sixteenth century. At this time, the Monarchia Hispanica ruled by Philip II of Spain was Europe’s most powerful composite monarchy, with an empire that stretched from Europe to the Americas and South-East Asia. One of the ways in which the Castilian monarch displayed his power and authority was through architecture and artistic display. The way the empire saw itself, and the manner in which it wished to be seen, was thus projected in a number of buildings in Iberian cities. Therefore, the basic premise of the thesis is to consider how the idea of ‘empire’ affected the way the Castilian monarch saw himself as ‘ruler’ of a ‘global empire’. This thesis explores these ideas of empowerment through a number of case studies that reflect the way the ‘centre’ of the empire was affected by Universal Monarchy. With Madrid as the capital of this empire from 1561, the Castilian monarchy designed new spaces in the old city that were intended to echo imperial glory. Philip II regulated the building fabric in the city to conform to a universal and homogeneous imperial city model that had been implemented in the Indies in previous decades. This is precisely the focus of the first case study, with a new approach to understanding the debated decade of the 1560s in the urban history of Madrid. I propose a novel perspective on the utopian planning of Madrid, through comparison with urban legislation enforced in other domains of the empire. Philip II’s empire was ruled through the written word, with a highly specialised and sophisticated bureaucracy. This bureaucratic character was mirrored in the architectural reforms of Simancas fortress to adapt it for archival needs. The archive in Simancas is the second case study: this is a multi-layered examination of cultural and political history and how this was reflected in the spatial configuration of the new archival chambers. I identify a hitherto unknown European vernacular tradition in the architecture of the incipient sixteenth-century regal archives. The architectural expansion in the fortress contextualises the crucial role that the archives played in the expansion and cohesion of the composite monarchies under Philip II’s rule. As the supremacy of Philip as ruler of a global empire was emphasised both through the arts and propaganda during the union of 1580, the celebration of the union of Portugal with the Monarchia Hispanica is the focus of chapter three: the joyous entry of the ruler into Lisbon in 1581. I demonstrate how sections of this entry were clearly designed to evoke the imperial vision defined at Philip II’s court, while other ephemeral displays were the result of local traditions. The interaction of both realities is critical for comprehension of how the monarch wished to be seen in his new realm, and of the difficult relationships between the ruler and the ruled. This imperial dominion was also displayed architecturally in significant regal buildings, such as the Monastery of El Escorial, the most paradigmatic example of the Austriaco style created under Phillip II’s rule. The final part of this thesis examines a chamber in this building: the Hall of Battles. This chamber is ornamented with impressive frescoes representing victorious battles. I explore the themes emerging from the Hall of Battles, such as the war against heresy and infidels, the propagation of faith and the Spanish hegemony in Europe, amongst others. These themes were treated in many of the chronicles, sermons, and eulogies printed in Madrid and throughout the empire. By examining how these are narrated in the funeral chronicles, I consider how the ruler wished himself to be portrayed in his kingdom upon death. In short, all these case studies explore from diverse perspectives and locations how Spain’s imperial expansion during the sixteenth century allowed Philip to project and communicate an image of himself as the monarch of a worldwide empire through art and architecture.