Problem statement: The beauty of Iranian ancient architecture is still an essential question, which has invited numerous investigations. This requires even further contemplation in the milieu of present esthetic crisis in contemporary architecture and the associated vacancy of theory, particularly when our contemporary architecture is lacking any relevance to categorical beauty from the viewpoint of Iranian thought and architecture. Many studies inherent in the religious literature and the textual works by Islamic thinkers have attempted to deal with and explain this question. However, the only authentic sources to elicit and reveal the hidden layers of beauty are undoubtedly the remaining artistic works. Research objectives: This study of Khaju Bridge, an authentic work remaining from the Safavid era, attempts to elicit the ontological foundations of beauty in this artwork and reveal how beauty has found its embodiment and form in the architecture of this building. Research method: The phenomenological approach was adopted to disclose the nature of beauty and the lived experiences of four groups attending the bridge were studied under the influence of Max van Manen. Conclusion: The findings suggest that contemporary architecture is no longer able to create beautiful and exhilarating spaces due to its lateralization towards form, function, or meaning. Indeed, architecture is beautiful when it can properly respond to the triad of form, function, and meaning. Moreover, seven components, i. e. vividness, selflessness, originality-authenticity, artistic richness, logicality, poetry, and thought-wonder, were identified as the ontological constructs of beauty in Khaju Bridge, to be used to create beautiful spaces in the process of their transformations into various structures.