Erected between 1612 and 1638 in Isfahan’s central plaza, Maydan-i Naqsh-i Jahan, the Shah Mosque was in all likelihood the first congregational mosque built by a ruler of the Safavid dynasty. An inscription on the mosque’s portal refers to the building as a congregational mosque erected by the order of Shah Abbas (r. 1587-1629). In popular parlance, however, the mosque was primarily known as masjid-i shah (the Shah Mosque). The ambivalent status of the mosque was caused in part by the presence of a formidable counterpart at the heart of the pre-Safavid Isfahan: i.e. the long established Friday Mosque, which despite the grandeur and opulence of its new rival never lost its status as the Friday Mosque of Isfahan. This essay analyzes the expressions, perceptions, and performances of urbanity and sacredness in and around Isfahan’s dual Friday Mosques in the seventeenth century. It shows how the Shah Mosque’s designated function as a venue for “congregational prayer” was overshadowed by its aesthetic charm, by its associations with specifically Shi?i themes and practices, and by its character as a space for representation of royal authority. The paper particularly focuses on the design and iconography of the monumental portal of the Shah Mosque. Moreover, drawing on unexplored Safavid literary sources, the essay analyzes the perceptions of the mosque by contemporary viewers. Rather than referring to the mosque as a place of communal prayer, Safavid poems highlight the mosque’s visual qualities and uncanny atmosphere. The analysis of the Shah mosque in relation to the space of the Maydan shows that the mosque proper was not the sole locus of pious veneration: the mosque’s portal in conjunction with other sites around the Maydan shaped a network of religious practices which did not fit into a strict dichotomy between the mosque and the urban space. Furthermore, comparing the urban context of the two Friday mosques of Isfahan reveals how their accessibility and degree of integration in the city’s spatial structure affected their function as public urban spaces. Unlike the Shah Mosque, the Old Friday Mosque was spatially integrated into the surrounding urban fabric and could be accessed from multiple entrances. These contrasting urban contexts gave each mosque a distinct character: the Shah Mosque was associated with royal might and visual pleasure, while the old Friday Mosque was the locus of popular piety and everyday practices of the city’s ordinary residents.