In this article by reviewing the environmental aesthetics experience, natural townscape, and ecological assessment related concepts, ecological assessment is known as a process that pave the way for achieving a positive (pleasant) experience of natural aesthetics in natural townscape. In fact, it seems that ecological assessment and evaluation of the natural context should be the fundamental part in the process of urban design of large scale projects, which are developed to improve the quality of environment aesthetics experience. Since, ecological assessment of the context contributes to analysis and evaluation of those elements and aspects of the environment that provide human with better concentration to obtain more pleasant aesthetic experience. In this study, by performing ecological study, analysis, and assessment of the natural context of Darabad valley’s river, as one of the central urban and natural landscapes in Tehran, approaches and policies that are related to environmental aesthetics in this natural townscape are developed. These approaches and policies highlight better rehabilitation and restoration of the context of valley’s river, as a human real and public space; preservation, improvement, and understanding of ecological and biological resources; and increase of visual quality and enrichment of views and vistas in the river’s bed. The present analytical-descriptive case study has used several research methods such as literature, references, and visual documents review, and observation and simulation in the context of library and field investigations. key word: Environmental Aesthetics, Aesthetic Experience, Natural Townscape, Ecological Assessment, River of Darabad Valley.