The document provides an overview of architecture from the Early Christian period through the Gothic era. It begins by discussing how the Roman Empire split into eastern and western halves in 400 CE. Christianity had become the dominant religion. As new rulers came to power, architectural styles evolved from Early Christian to Byzantine under Constantine, and then to Romanesque. Key events and developments discussed include Constantine moving the capital to Constantinople in 330 CE and constructing Hagia Sophia, the fall of the Western Roman Empire in 410 CE, and the emergence of Gothic architecture in the late medieval period. Stylistic elements of Early Christian, Byzantine, and Romanesque architecture like semicircular arches, vaulting techniques, and basilica