Localities at the southern end of Lake Päijänne (IENDE LACUS) are mentioned on maps, such as ANIENPELTO (Anjanpelto), SYSME (Sysmä), ACHAUPE (Akaanpää) and ASKALA (Asikkala). Details of the northern end of Lake Päijänne slowly begin to emerge. JEMSE or Jämsä is more or less in the right place, similarly the centre of the administrative parish of Rautalampi (RAUTALAMBI) which encompassed almost all of Central Finland and KONNAVESI (Konnevesi) which was incorrectly located on the wrong side of the watershed.

For makers of maps the relatively narrow Lake Päijänne, which runs in a north-south direction, was a highly useful feature. The shape and size of Lake Päijänne acquired the correct dimensions far earlier than Lake Saimaa, for instance, which caused mapmakers grey hairs right down to the 19th century.