There are, in certain corners of the Internet, people out there who believe that the Smithsonian Museum are covering up evidence that Ancient Egyptians came over to the Grand Canyon in North America, leaving hieroglyphs and mummies hidden for thousands of years.
The conspiracy theory goes back further than most, to 1909 when readers of the Arizona Gazette were treated to the tale of explorer "G.E. Kincaid" and his trip down the Colorado River. The paper ran two stories about the trip, and in the second he tells of how he saw a cave entrance about 609 meters (2,000 feet) above the river bed and hiked up to explore.
"When I saw the chisel marks on the wall inside the entrance, I became interested, securing my gun, and went in," he reportedly told the paper. "During that trip, I went back several hundred feet along the main passage till I came to the crypt in which I discovered the mummies."
"The tomb or crypt in which the mummies were found is one of the largest of the chambers, the walls slanting back at an angle of about 35 degrees. On these are tiers of mummies, each one occupying a separate hewn shelf. At the head of each is a small bench, on which is found copper cups and pieces of broken swords. Some of the mummies are covered with clay, and all are wrapped in a bark fabric," Kincaid said later in the article. "It is worthy of note that all the mummies examined so far have proved to be male, no children or females being buried here. This leads to the belief that this exterior section was the warriors' barracks."
According to the report, the mummies were not alone. He grabbed a number of relics – taking from the Indiana Jones archaeological playbook – and left, shipping them off to Washington. Going further inside, he discovered large areas and rooms chiseled out of the rock.
"Over a hundred feet from the entrance is the cross-hall, several hundred feet long, in which are found the idol, or image, of the people's god, sitting cross-legged, with a lotus flower or lily in each hand. The cast of the face is oriental, and the carving this cavern," Kincaid reportedly said. "The idol almost resembles Buddha, though the scientists are not certain as to what religious worship it represents. Taking into consideration everything found thus far, it is possible that this worship most resembles the ancient people of Tibet."
The report claimed that Kincaid had found a number of other artifacts, including vases, urns and copper and gold cups, which the Smithsonian was investigating. Weirdest of all these unusual finds were the hieroglyphics.
"On all the urns, or walls over doorways , and tablets of stone which were found by the image are the mysterious hieroglyphics, the key to which the Smithsonian Institute hopes yet to discover. The engraving on the tables probably has something to do with the religion of the people. Similar hieroglyphics have been found in southern Arizona. Among the pictorial writings, only two animals are found. One is of prehistoric type."
As the old saying goes, extraordinary claims require extraordinary evidence. Unfortunately, this claim barely has what you'd call tenuous evidence. The Smithsonian of course denies that they were involved in any such find, and further states that there are no records confirming Kincaid even exists.
It's probable that the tale was a hoax. A similar tale had been spun in 1878, when noted hoaxer Joseph Mulhattan claimed that a giant cave had been opened in Kentucky, with several Egyptian mummies found inside. This was actually a pretty mundane claim for Mulhattan, who had also said that the star of Bethlehem had been rediscovered, and that George Washington's body had turned into stone after he died.