That picture shows the lower half of the Lunar Module, the part that stayed behind on the Moon when Armstrong and Aldrin blasted back up off the surface. It was essentially dead weight, so the LM was designed to split in half, with the top half (the aptly-named Ascent Module — click on the diagram on the right for details) going back up into orbit to meet with Michael Collins in the Command Module. From there they returned to Earth.
The Descent Module is about 4 meters or so across, and the image, above taken when the Sun was low on the horizon, clearly shows the DM and its shadow cast across the lunar surface. The region where they landed was fairly smooth, so the module is the only thing large enough in the image to cast an appreciable shadow.