[Docere]

Orthodox Jews have to live close to their synagogues, so they tend to be very clustered in these areas. Any major Orthodox Jewish area in a city is going to be among a city's most religious.

Muslims would be more separated residentially by nationality, and immigrants from certain Muslim countries are more likely to be religious than others. For example, immigrants from Pakistan are more religious than those from Iran (and the vast majority of Pakistani immigrants here in Toronto are Muslim - a significant minority of those from Iran are not and fewer of the Muslims are very religious).

A Hispanic neighborhood or white ethnic Catholic neighborhood is going to have at least a good number of religious Catholics, but they live alongside a lot of less religious Catholics too.

Black neighborhoods - whether African American or Caribbean - all have a significant number of born-again or evangelical churches (Baptist or Pentecostal).