For 17 th and 18 th century Europeans, the territory of Russia, especially its eastern parts neighboring China and Central Asia, were largely terrae incognitae. Maps and detailed geographical knowledge of the area had strategic significance for countries and governments and were often handled with secrecy. Among the foreigners invited to Russia by Peter the Great was the French astronomer Joseph Delisle, who subsequently played a leading role in establishing scientific astronomy in the country and participated in some cartographic projects. Clandestinely, Delisle spent much of his time copying maps and geographical materials by other Russian geodesists, which he then took with him to France. The Delisle collection in Paris is of great historical importance as it includes many documents that have not survived in Russian archives. It has been studied by Konstantin Salishchev and Garriy Utin. This essay draws attention to some previously overlooked Russian sources from the Paris collection, in particular textual documents rather than maps. These include: 1) pre-Petrine geographical and historical descriptions of Eurasia; 2) projects for the mapping of the Russian Empire; 3) adopted methods and procedures of geodesic and cartographic work; 4) lists of existing maps; 5) materials of the First and Second Kamchatka expeditions; and 6) Russian and Chinese materials related to the border treaty of 1689, including a copy of the first Chinese (Jesuit) maps of Amur and the Maritime Provinces (1706-1711), officially presented to the Russian government by the Chinese authorities in the 1720s. It is hard to overstate the historical and geographic importance of these documents, which should become the topic of a joint Russian-French research project leading to a bilingual publication.