This communication proposes a methodical approach trying to link the concept of “Windows to the Universe” to the uses of the Criteria defined by the World Heritage Convention (UNESCO 1972). The first issue is well advanced today after more than 10 years of active studies and preservation projects such as “Starlight Reserves” by specialists of astronomy, archaeoastronomy and environmental sciences. The second issue is related to a UNESCO Convention ruled by the WH Committee that has led to the recognition of around 1000 World Heritage sites over 40 years. The official booklet Operational Guidelines for the Implementation of the World Heritage Convention (latest edition 2015) (UNESCO 2015) summarizes conceptual ideas and methodological recommendations for WH nominations. In practice the WH Committee's decisions rely on the scientific and professional evaluation of each site by UNESCO's advisory bodies: ICOMOS for cultural heritage and IUCN for natural heritage. The first goal of this presentation is to establish appropriate understanding of a very specific conceptual approach (Windows to the Universe) in the context of a very large UN Convention (the World Heritage List) related both to cultural and natural heritage in general. The second goal is to give a readable understanding of the WH requirements coming from the strict evaluation of the “Outstanding Universal Value” (OUV) of a given place, including the choice of WH Criteria expressing OUV with respect to the format of the Guidelines . Furthermore, and due to concepts coming from two very different fields, the communication aims to present a practical methodology in the case of a possible WH nomination: how to understand relationships between different classes of value and how to demonstrate OUV and justify the choice of Criteria for the place. Beyond potential WH projects, obviously limited in number, the communication tries to propose an efficient and general methodology for assessing the value and creating understanding of places having a “Windows to the Universe” facet.