Final answer:
The building of structural mosques began in the 8th century AD with notable examples, such as the Great Mosque started in 786 AD in Cordoba and the Umayad Mosque completed in 715 CE.
Step-by-step explanation:
The building of structural mosques began in a) 8th century AD, specifically with the construction of the Great Mosque in Cordoba, Spain, which was begun in 786 AD. Key developments in the architecture of mosques include features like the hypostyle hall, which can be seen in the Great Mosque at Cordoba, started in the same period. Notably, the Umayad Mosque, one of the earliest mosques, was completed in 715 CE, during the Islamic Golden Age, indicating the beginning of mosque construction even before the 8th century.
A specifically recognizable Islamic architectural style emerged combining Roman building traditions with local adaptations of Sassanid and Byzantine models. The foundational mosques, such as Muhammad's house in Medina, were both places of prayer and community meeting spaces. The Dome of the Rock in Jerusalem and the Umayad Mosque in Damascus are prime examples of Islam's early architectural identity.