Maps
The Cartographic and Geological Institute of Catalonia. Maps and aerial photography in low and high resolution. Old and modern material from all over the world. Terms of use.
National Center for Geographic Information. Old and modern maps and images in high-resolution. Attribution is required. Check the Legal notice section.
There are several resources that collect old and modern maps and images. Always check the indications of each page on copyright.
Perry-Castañeda Library Map Collection.Includes over 250,000 maps, although only a part is available online. Information on copyright.
David Rumsey Map Collection. Historical maps that can be used for free, as long as it is not for commercial purposes. More information.
Visible Earth.Satellite images that can be used for free, but it is necessary to check the specific conditions of each document. More information.