An image viewing system comprising - a database, the database containing a plurality of aerial images of a geographical region that is divided into tiles, an aerial image covering an geographical area of a tile, wherein when the aerial image shows an urban agglomeration that is delimited from a surrounding geographical area by an outer boundary, the aerial image is configured such that an aerial view of the urban agglomeration shown in the aerial image is limited to the urban agglomeration, wherein no aerial view is shown of the geographical area outside the outer boundary, wherein the geographical area covered by one tile contains two different urban agglomerations (51, 52), the database containing a first aerial image of said one tile showing the aerial view being limited to one of the two urban agglomerations, the first aerial image showing no aerial view of the geographical area outside the outer boundary of said one urban agglomeration, the database containing a second aerial image of said one tile showing the aerial view being limited to the other of the two urban agglomerations, the second aerial image showing no aerial view of the geographical area outside the outer boundary of said other urban agglomeration, wherein the aerial image is a digital aerial image in which the pixels of the aerial image each contain at least one colour value and a transparency value varying from a value corresponding to full transparency to a value corresponding to no transparency, wherein the aerial image is configured such that the transparency value of pixels outside the urban agglomeration is set to full transparency, and the transparency value of pixels inside the urban agglomeration is set to no transparency, - an image viewer generating a display image of the aerial image, wherein, when the image viewer determines that a display image is to be generated for a geographical region for which two different aerial images exist, the image viewer generates the display image comprising two different urban agglomerations by superpositioning the two different aerial images (51, 52) of said geographical region from the database, and by displaying them at the same time. - a database, the database containing a plurality of aerial images of a geographical region that is divided into tiles, an aerial image covering an geographical area of a tile, wherein when the aerial image shows an urban agglomeration that is delimited from a surrounding geographical area by an outer boundary, the aerial image is configured such that an aerial view of the urban agglomeration shown in the aerial image is limited to the urban agglomeration, wherein no aerial view is shown of the geographical area outside the outer boundary, wherein the geographical area covered by one tile contains two different urban agglomerations (51, 52), the database containing a first aerial image of said one tile showing the aerial view being limited to one of the two urban agglomerations, the first aerial image showing no aerial view of the geographical area outside the outer boundary of said one urban agglomeration, the database containing a second aerial image of said one tile showing the aerial view being limited to the other of the two urban agglomerations, the second aerial image showing no aerial view of the geographical area outside the outer boundary of said other urban agglomeration, wherein the aerial image is a digital aerial image in which the pixels of the aerial image each contain at least one colour value and a transparency value varying from a value corresponding to full transparency to a value corresponding to no transparency, wherein the aerial image is configured such that the transparency value of pixels outside the urban agglomeration is set to full transparency, and the transparency value of pixels inside the urban agglomeration is set to no transparency, - an image viewer generating a display image of the aerial image, wherein, when the image viewer determines that a display image is to be generated for a geographical region for which two different aerial images exist, the image viewer generates the display image comprising two different urban agglomerations by superpositioning the two different aerial images (51, 52) of said geographical region from the database, and by displaying them at the same time.