This paper carefully explains Pirnia’s theory regarding the orientation of traditional Iranian cities and buildings (Roon) and investigates the factors involved in this historic architectural phenomenon. For this purpose, 40 traditional Yazd Qajar houses were under study. Most of which are in the Rasteh Roon and close to the southwest direction, and only five contradict the direction that Pirnia had pointed. While the primeval data indicated the theory is strengthening, the investigation followed the fundamental factors behind this event. From the perspective of analysis and discussion on involved factors (climate, topography, aqueducts, urban arteries, politics, trade routes, privacy, noise, view, and religion), it turns out that the direction of the wind and sun had negligible impacts on this orientation, and architects of the Qajar era in Yazd old city did not care about these climate factors. It seems religious factors were more influential. Thus, despite being approvingly referenced in many scientific studies, Pirnia’s orientation theory (Roon)—the efforts of past Iranian architects to orient buildings in a specific direction due to their unique knowledge of region and climate factors—becomes not solid.