This chapter explores the handling of natural light in the classical Greek temple and the Byzantine church. It discusses concepts of orientation as related to their respective functions and aims and the planning of lighting. It addresses light’s influence on the shaping of formal components in the Greek temple, such as the peristyle, fluting, and echinus of the Doric column. It attempts to establish relationships between the temple and the church layout in both plan and section, on the basis of light considerations connecting these observations to the widespread scientific interest of the period in the nature and behaviour of light. It discusses Byzantine church lighting planning, focusing on the church of Hagia Sophia of Istanbul, in an attempt to provide a perspective of relevant concepts in philosophy and theology, and to understand the development of the aesthetics of light and space within it.