The Valley of the Kings was used as a burial place for the Pharaohs in the New Kingdom. The ancient Egyptians gave up the pyramids, because they were too conspicuous and easily robbed. They hoped they could keep the tombs intact if they could be hidden in this valley. It worked for only one of the tombs, the one of Tutankhamun (1336 - 1327 BCE), and even that one not forever, only for 3249 years till 1922. Tutankhamun was actually a very minor Pharaoh who died very young. Imagine the treasures that would have been in the tombs of Pharaohs like Ramesses II.
The tombs were cut in the rocks and hidden. Some accounts say that the workers who dug the tombs were executed after they were done to keep the location secret. I somehow doubt that because the tombs were built over long periods of time, many years. I don't see how you could keep the workers separate for that long and then execute them.
One of the first things people ask is what the chances are to find a tomb, like Tutankhamun's, that has not been robbed. The answer is zero chance. We have accounted for the tombs of all Pharaohs, there are none left to be discovered. But there are still other things to be discovered, just recently several mummies were found in the valley of the kings, though not royal mummies.
The tombs themselves are breath taking. They are lavishly decorated with paintings throughout the whole tomb. All the colors are still vibrant, due to the fact that the ancient Egyptians used only mineral colors, no organic colors. Unfortunately you are not allowed to take pictures in the tombs. I can only show scans of a few postcards of some tomb paintings.
Osirisnet.net has detailed descriptions of many of the tombs around Thebes (Luxor) in the Valley of the Kings.
The mountain overlooking the Valley of the Kings looks like a pyramid. This is presumably part of the reasons why the ancient Egyptians chose this valley. It is a reminder of the pyramids that used to be the burial places of the Pharaohs. (756k) Painting in the tomb of Amun-her-khepeshef, a son of Ramesses II. (557k) Entrance to the tomb of Ramesses VI. (586k) Entrance to the tomb of Ramesses VI, showing the God Osiris twice above the entrance. (580k) Ceiling paintings in the tomb of Ramesses VI, showing the Goddess Nut twice in her characteristic pose, arched over the earth, with stars on her body. (639k) Details of ceiling paintings. (855k) Front part of the painting of Nut, arched over the earth. (651k) Sarcophagus of Ramesses VI with the golden mummy case. In the background is the God Osiris (left), receiving the Pharaoh. (650k) Interior of the tomb of Ramesses VI. (550k) Paintings in the tomb of Tutankhamun. The scarab beetle symbolizes resurrection. The baboon could be the God Thoth. He is sometimes represented as a baboon, and symbolizes wisdom and the scribes. He was the recorder of the ceremony of the Weighing of the Heart (see Egyptian Mythology). (629k) Golden Mask of Tutankhamun. (448k) Painting in the tomb of Seti I. It shows the God Sokar receiving the Pharaoh. (500k) Ceiling paintings in the tomb of Seti I. (554k) Sarcophagus of the Pharaoh Seti I. (512k) Superb paintings in the Tomb of Horemheb, showing the God Horus (center right) and his wife Hathor (left). (665k) More superb paintings in the tomb of Horemheb. (662k) Sarcophagus of the Pharaoh Amunhoteb II. (407k) Interior of the tomb of Pharaoh Taweseret. (594k) Golden statue of the God Ptah from the burial treasure of Tutankhamun. (345k) Alabaster lid of one of the canopic jars of Tutankhamun. (556k) Golden leopard head from the burial treasure of Tutankhamun. (453k) Golden double vase from Tutankhamun's tomb. (633k) Alabaster statue of an ibex from Tutankhamun's tomb. (549k) Sculpture of Tutankhamun's head. (493k) Golden stature of Tutankhamun fishing on a reed boat. (524k) Golden statue of the Goddess Serqet. (383k) Golden breast ornament from Tutankhamun's tomb. (536k)