This shapefile represents the uncertain political borders of Europe for the year 900. Uncertain borders are areas centered between political territories representing uncertain political boundaries. The bigger an area, the higher the uncertainty is for this border. This layer is part of the Euratlas Georeferenced Vector Data collection that is composed of 21 maps, one for each century from year 1 to year 2000. These maps depict the detailed political situation of Europe at the first day of each centennial year C.E. from year 1 to 2000. Each map is composed of two kinds of layers: physical features layers, such as seas and rivers, and political features layers, such as states and cities. Some layers also cover adjacent portions of North Africa and the Middle East.