National Geographic Institute mapping as a source for the historical documentation of the public works heritage and the built landscape

The maps from the National Geographic Institute show nowadays, and for the first time, a complete and detailed image of a large part of Spain from the end of the 19th century to the beginning of the 20th. These maps were drawn up from direct work on the ground, according to previously established uniform criteria, so they are an exceptionally interesting source of historical information. Basing on our wide-ranging experience of working with these documents, this paper intends to demonstrate their ability to contribute to the documentation and assessment of heritage properties related to public works and of the various milestones that connected the built landscape during that period.