"In Civilization IV, a cathedral is defined as an especially large and ornate religious building where the faithful worship. Only the most prosperous cities can afford to create cathedrals, as they require huge amounts of raw material and years of dedicated labor by skilled craftsmen. For example, the Notre Dame Cathedral in Paris, France, took over two centuries to complete.
In common usage, the term "mosque" is used to describe any Islamic house of worship. In this game that term is reserved for the more important and impressive structures; common mosques are called "Islamic temples." The first mosque built was the "Kaaba," in Mecca, which resides inside of the the Masjid al-Haram. According to tradition, the Kaaba was originally a temple constructed by the prophet Abraham and his son, Ishmael. By the Prophet Muhammad's time, the Kaaba was being used to worship many "false" gods; he destroyed the idols and rededicated the structure to Allah when he captured Mecca in 630 AD."
In the city screen press the following icon to start Islamic Mosque construction: