"Atlas Fontium" is a website dedicated to the publications of historical sources and materials from the period of the old Poland and the old Republic of Poland that have a spatial dimension and as such can easily be published together with a map. The main purpose of the project is to create a uniform system for gathering, analysing, and making available of information and sources for research in the field of historical geography of Polish lands within borders prior to 1772. The results of historical and geographical research conducted in various scientific centres, in Poland and abroad, will be presented on an IT platform. The project is based on the framework of settlement network and territorial divisions, both church and secular, in the period before the Partitions. As such, its main aim is to present materials related with this period. "Atlas Fontium" is not a publication, but rather a place for publishing authors' own source editions and studies. Preliminary declaration of the scientific society interested in modern methods of presenting results of their geographic and historical research gives hope that the platform will be quickly supplemented with new materials, particularly of the Historical Atlas of Poland (Institute of History of the Polish Academy of Sciences), as well as the Atlas of Religions and Confessions in Poland in the Polish-Lithuanian Commonwealth (Institute of History of the Catholic University in Lublin).