The Pero dune field is one of the largest in southeastern Brazil. Besides possessing Quaternary eolic records relating to the semiarid climate of the region, it also contains archaeological sites and functions as a haven for endemic animal and plant species, some of which are endangered. The dune field is of hydrogeological and pedological importance, not to mention being a site of undeniable natural beauty. The area has been targeted by the real estate industry and could disappear due to international tourism-based projects. The aim of the study reported here is to demonstrate the relevance of this site as a geological and geomorphological heritage site according to international methodologies used for such evaluations and through a comparison of the results obtained here with those in the inventory of the other geosites contained in the Cabo Frio Tectonic Domain. The results show that the area is relevant in four key areas, namely, science, culture, education and tourism. They also highlight the frailty of this geodiversity unity, which was constructed through the actions of the wind and which has an important ecological function as a biodiversity substrate and aquifer. The ultimate goal of the study is to use these results as arguments for the preservation of the area.