The Omega Project: Achille and Pier Giacomo Castiglioni’s Last Lesson on Architecture and the City

The Omega Centre (1967–1970) represents a remarkable yet largely overlooked achievement by Achille and Pier Giacomo Castiglioni. Situated directly on Milan’s Piazza del Duomo, the project distinguished itself amid the contemporary proliferation of shops and showrooms that emerged in the final years of Italy’s economic boom, thanks to the originality of its spatial and material solutions. In this sense, the Omega Centre stands as one of the Castiglioni brothers’ most refined architectural works–and, notably, the last they completed together. Despite the attention it initially drew from critics both in Italy and abroad, the Omega Centre has since remained on the margins of scholarly interest, overshadowed by the Castiglionis’ celebrated contributions to industrial design. Its commercial nature and eventual dismantling in the 1980s may have further contributed to its neglect, limiting both critical and scholarly engagement with the project. Yet the significance of the Omega Centre lies precisely in its ability to reflect the urban context it inhabits. It embodies a combination of interpretation and innovation, where materials and form engage in an open and synergistic dialogue – becoming, in turn, a lens through which to read the Milan itself. Drawing on extensive archival research and previously unpublished materials from collections in Italy, Switzerland, and Japan, this paper aims to address that historiographical gap by critically reconstructing both the Castiglioni brothers’ design process and the building’s relationship with the city. The analysis unfolds across multiple scales – from the urban setting of Piazza del Duomo to the detailed design of interiors and objects, and back again – offering a coherent narrative that links object-scale innovation with urban meaning. Ultimately, the paper delivers a compelling lesson on the responsibility of commercial architecture – and of architecture as a whole – in shaping and interpreting the contemporary city, standing as the final statement to the Castiglioni brothers’ enduring legacy.