This article critically analyses the proliferation and production of what we call “religious maps” in Europe in recent years. Religious maps have emerged as a form of monitoring, describing, and representing spatial processes of (ethno-) religious diversification. Through the comparative empirical analysis of the cases of Barcelona, Hamburg, and Amsterdam, we demonstrate that maps and the knowledge formations they (re)produce have become key tools to govern religious diversity in contemporary Europe. Counting, mapping, and categorizing places of worship provides allegedly objective and stable knowledge about increasingly complex and dynamic religious practices. Religious maps also make religion “legible” for the state through the classification of places of religious practice according to historically contingent categories of religious traditions and groups and by (re)producing what Brian Harley calls “cartographic silences”. As such, the practice of mapping religions necessarily reduces the complexity of transnational and translocal social reality. This produces particular forms of intelligibility and representational hierarchy through which policy-makers and citizens in general understand religion in cities. The article shows that the analysis of the ways maps are conceived, produced, and circulated offers a distinctive lens through which to explore entanglements of knowledge, media, and power in the contemporary making of social, political, cultural, and religious landscapes.