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Abell 2218
Abell 2218 is a cluster of galaxies. It is at a distance of about 2 billion light years behind the constellation Draco. This is the 2,218th cluster in George Abell's catalog. It has come under a lot of study recently. When deep images are taken of this cluster, beautiful arcs are seen surrounding the center of the cluster (Abell's images were relatively shallow, so these arcs were not visible to him).

Most of these arcs are actually images from a single galaxy far behind the cluster! When the light from this galaxy (5-10 times more distant than Abell 2218) passes through the cluster, the light gets deflected by the gravitational field the cluster. In this case (which is rare) the light is bent so stronly that the image is sheared out into an arc. Also, because of the strength of the lens, light passing to either side of the cluster gets bent toward the observer and multiple images are seen. Because some of the arcs are blue and some are red, I suspect the arcs may be from more than one background galaxy, perhaps in a cluster or group of their own. You can learn more about this picture by going to the NASA Press Release for this Hubble Space Telescope image. Other press releases can be found here.