Complex sentence: The great cathedrals of the Middle Ages during the Gothic Period of ecclesiastical architecture formed the inspiration for this particular architectural style; not only in residential buildings, but in many commercial structures, churches and cathedrals built during this time.
Split into simpler sentences: The great Cathedrals of the Middle Ages during the Gothic Period of ecclesiastical architecture formed the inspiration for this particular Architectural style. Not only in residential buildings, but in many commercial structures and, Churches and Cathedrals built during this time.