What if the pyramids actually weren't built by the Egyptians?

The title is pretty self-explanatory, but in the past few decades we've discovered that the pyramids aren't Egyptian at all. We can't find any traces of the ancient Egyptian race anywhere near the pyramids. No remains of mummies, no bones or skeletons. There's no hieroglyphics either, just some sort of other language that nobody has been able to decipher.<br><br>The pyramids were built in the 20's of the fourth century BC, but we've found that there is no way the ancient Egyptians could've built them in that amount of time. It would have taken centuries to build those things. The mummification process was also discovered to be far more ancient then we previously thought. It was found that it took years to do. Not days, but years.<br><br>So, who built these things? We have no idea. The only clue we have is that one of the pyramids is aligned perfectly with the constellation Orion. It's pretty creepy to look at one of these bad boys at night with all the lights off.<br><br>Later, it was discovered that the sphinx is actually older than the pyramids. If you look at the sphinx you will notice that the people in the picture are wearing turbans. The Sphinx has the same alignment as the pyramids and is also aligned to the constellation of Orion. So, who built the pyramids and the sphinx? Where did they come from? Why did they disappear?