Theologically speaking, mosque architecture is insignificant since a masjid is simply a clean, oriented, and conducive place for prayer. As phenomena in the US and Britain, however, the architecture and de´cor of purpose-built and storefront mosques reveal the status of relations with the host society as well as the identity and aspirations of the community within. This article begins by briefly reviewing the major historical and regional styles that influence the building of immigrant mosques in the US and Britain. The meanings of domes and minarets are analyzed, as well as their increased importance in diaspora as exposed decorous elements. There are three types of mosque architecture in the US and Britain: internationalist-inclusive, internationalist-exclusive, and regional-exclusive. Each articulates a theological interpretation of ummah and dawah, or the degree of internal inclusivity and outreach to non-Muslims. The number of mosques in both the US and Britain tripled during the 1990s despite obstacles of religious prejudice, though most building projects have been put on hold since the attacks of September 11, 2001.