The reflection on sacred places continues to assume significant relevance today in urban space production. The public value of sacred buildings has consolidated over time an aggregating sense of community, representing spaces for meeting and sharing. Their historical relevance as spaces for meditation represents for mankind places of personal reflection, while they have always played an important role in the city and in its symbolic and spatial structure. Thus, starting from the hypothesis that the sacred space is affirmed as an interface, because it welcomes the individual and serves the community, we examine the architectural features that enhance this ambivalence, exposing transition systems between private and collective spaces, seeking to systematize essential composition matrices for new urban spaces for public use. Assuming Lisbon as a framework, this article proposes a comparative reading between two paradigmatic buildings—Sagrado Coração de Jesus Church and the New Mosque of Lisbon—with similar goals according to the relationship between architecture, place sacrality, and the urban public space. Methodologically, drawing is used as an interpretative tool and, through formal decomposition, this article tries to demonstrate that these buildings are the result of a reflection deeply determined by the value of the place’s identity in the city’s public space system. According to these case studies, sacred buildings are conceived based on formal and spatial links that are rooted in Lisbon’s urban layout. It is sacred buildings that are at the origin of urban places for public use. Each one of these buildings share an idea of architecture with an urban and public role which integrates the objects with the shape of the city and contradicts the tendency for the dissociation between urban elements. In a way, they can be considered paradigmatic examples of architecture with an urban vocation.