One of the fundamental notions of realization of sustainable city within the framework of the theory of sustainable development is what affects the urban green spaces as well as the influence they may have. As the upshot of years’ worth of experiences in the ideology of Iranian urban design, Iranian garden is of magnificently high position which possesses the potentials to act as the green space with a variety of functions to serve the promotion of sustainability in today’s cities. Closely studying Dolat Abad garden as one example of the exquisite Iranian garden architecture in a comparative analysis, this study exامینes the role of gardens in the achievement of today’s cities to sustainability within the frameworks of the theory of sustainable city. It will also attempt to prove the hypothesis regarding that Dolat Abad garden and the Taj Mahal have established themselves as sustainable elements in the two contemporary cities of Yazd and Agra, and will accordingly continue to remain so.