This interactive map was made using a selective composition of Nicholas I's correspondence in the Regesta Imperii, resulting in a total of 287 entries on this map. The map has filters and is searchable, which may hopefully make it useful for those wishing to explore the data, and who can try different combinations of filters to see if anything interesting results from this. The methodology is explained more on Figshare (https://doi.org/10.6084/m9.figshare.19589902.v1)