Mannerism has for a long time been associated with primarily painting and sculpture. Its role in architecture has as a result been overshadowed, even though it offers a unique way of working with space. This thesis explores the question: “How did different Italian Mannerist architects use spatial manipulation to challenge Renaissance ideals and shape the viewer’s experience?” Through a comparative analysis of four Italian case studies—the Laurentian Library, Palazzo del Te, Palazzo Massimo alle Colonne and Villa Farnese—it becomes clear that Mannerist architects didn’t simply reject classical principles, but rather challenged their boundaries in their personal and inventive ways. While existing studies mostly discuss Mannerist architects separately, this thesis highlights the variation within Italian Mannerism itself by not only revealing their shared characteristics, but also the individual approaches. It shows that, aside from their differences, the Mannerists were united by a mindset of experimentation, challenging Renaissance ideals and the viewer experience. This approach includes unusual shapes and distortions like elongated proportions or irregular layouts. These were not simply random or decorative, but rather intentional and well-thought-out design choices.