Purpose and objectives of the study. The purpose of the dissertation research is to determine the Avestan orography and hydrography in Pahlavi sources with their further localization. With the advent of new materials, the author of the work again turns to the identification of the Hara Berezaiti mountains, the Ranha and Vahvi-Datia rivers and the Vorukash sea, and also, based on well-reasoned data, gives his own interpretation of these sources and determines the localization of Arianam-Vaija and the homeland of Zarathushtra.