A reflection on liturgical art and architecture, looking at the masterpieces of East and West that flourished in two millennia of Christian history. Today we are facing a "new iconoclasm" due to the lack of images in contemporary places of worship. The relationship between art and architecture, in the context of the Catholic liturgical space, is subject of debate among architects, artists and liturgists. Recently built churches have been subjected to fierce criticism or passionate defenses. The predominant role of architecture has reduced and sometimes canceled the possibility of complete and coherent iconographic programs, replaced by abstract decorations or even by white walls. To react to the contemporary crisis of art and architecture for worship, and rediscover figures and symbols related to the space and time of the liturgy, a group of experts draws on the lessons of past history, with particular attention to the Middle Ages, and investigates the more recent experiences in Italy, France and Serbia, bringing together representatives of Catholicism and Orthodoxy. The geographical, temporal and confessional breadth of the reflection is aimed at comparing different, even opposing points of view, in the desire to contribute in an innovative way to research on the capital theme of sacred space and its iconographic set.