The present dissertation is intended to be the first systematic investigation of the illusionistic pergola considered within the framework of the intellectual culture and the garden culture of early modern Rome. The subject is the fresco or mosaic decoration featuring a pergola – a depicted trelliswork covered with plants and peopled with birds – in the loggias, porticoes, and garden pavilions of villas and palaces in Rome and its environs. These pictorial fictions have survived in sufficient numbers to constitute a decorative trend, and moreover, appear in clusters at specific periods, which can be partly explained by means of the cultural factors predominant at the time. The dissertation discusses these pergolas in relation to antiquarian culture, the collecting of plants and birds, the study of natural history, garden furnishings and the art of treillage, thereby contextualizing them within the culture of early modern Rome. The dissertation assembles the first corpus of illusionistic pergolas in the period 1500-1620, updating a much earlier general corpus of 1967 by Börsch-Supan, and distinguishes three distinct periods of the proliferation of these pictorial fictions in Rome and its environs: the first period (1517-1520), the second period (1550-1580), and the third period (1600-1620). Important cultural issues relevant to each period are identified,and proposed as the frameworks for study. These include the reference to the antique and to the vernacular, mediation between indoors and outdoors, the tension between art and craft and the ambiguity of the pseudo-architectural, semantic and aesthetic cross reference between architecture and garden, and the reflection of the intellectual culture. On examination, the illusionistic pergolas are revealed to be a nexus of interrelationships between built structure, ornamented surface, garden and landscape, as well as multivalent embodiments of emerging ideas and sensibilities concerning the experience of architectural space and nature. By taking into account the middle ground of architecture and garden, the study explores the multivalence of ephemeral garden furnishings and their fictive counterparts, opening up a new perspective on the sites examined, and attempts to see a resonance of the tradition in modern times. / text