Most people are familiar with early cave paintings and their depiction of horses and bison.
There are also some Ice Age artworks that were made by carving images into rock. It would be boring to simply show a picture of a rock with a faint carving of a horse in it. Clicking on the rock makes a chisel sound and reveals the 26,000 year old artwork within. In 1996 when this feature went online, Java was the only technology available to accomplish this. Nowadays we would use Flash since it runs more smoothly.