Into the rabbit hole
Consider yourself warned: National Geographic's infinite photograph is addicting. Move the yellow square around the image, click, and you will zoom in to see a close up of the photos that compose that section. Each photo is a mosaic made up of hundreds of other photos (which are in turn mosaics themselves). Double click on any image to get more information about the photograph. All of the photos are user submitted, and there's a link that allows you to upload your own images for inclusion. It begs to have Louis Armstrong's What a Wonderful World playing in the background. Truly beautiful!