Comments:
Albert Einstein's General Theory of Relativity, published in 1916, predicted that massive objects, such as stars, could distort spacetime and hence bend the path of light rays passing nearby. This prediction was verified by the observation of such bending of starlight near the Sun in 1919. That same year, an English physicist, Sir Oliver Lodge, suggested that this phenomenon could produce a gravitational lens. In 1936, Einstein himself showed that, if a brightly-emitting object were exactly behind a massive body capable of making a gravitational lens, the result would be an image of a ring around the massive lensing object. However, he dismissed the possibility of ever discovering such a lens, because of the small chance that the precise coincidence required would ever arise.

Nevertheless, in 1979, optical observers discovered the first gravitational lens. The Very Large Array (a radio telescope in New Mexico, also known as the VLA) was quickly used to confirm the discovery.

The Einstein Cross is the image of a distant quasar whose light is lensed by a much dimmer foreground object. The quasar is not exactly behind the foreground object, so Einstein's perfect ring is not produced. Nevertheless, the alignment is so nearly perfect that multiple images of the quasar are produced.

In this picture, the multiple images of the quasar form a cross-like structure in the centre. More detailed pictures show the separate quasar images.