http://www.europa.com/edge/pyramid.html:

-Thirty times larger than the Empire State Building, the Pyramid's features are so large they can be seen from the Moon.
-Its base covers 13.6 acres (equal to seven midtown Manhattan City blocks), each side being greater than five acres in area.
-A highway lane eight feet wide and four inches thick could be built from San Francisco to New York and put inside the Great Pyramid.
-The oldest structure in existence, having been started 4,617 years ago, it is the sole remnant of the Seven Wonders of the World.
- It is built to face true North
- The Pyramid is located at the exact center of the Earth's land mass. That is, its East-West axis corresponds to the longest land parallel across the Earth, passing through Africa, Asia, and America. Similarly, the longest land meridian on Earth, through Asia, Africa, Europa, and Antarctica, also passes right through the Pyramid. Since the Earth has enough land area to provide 3 billion possible building sites for the Pyramid, the odds of it's having been built where it is are 1 in 3 billion
-The casing stones, 144,000 in all, were so brilliant that they could literally be seen from the mountains of Israel hundreds of miles away. On bright mornings and late afternoons, sunlight reflected by this vast mirrored surface of 5-1/4 acres distinguished the Pyramid as being visible from the moon. (Note: For those interested in possible symbolic significance, in Bible prophecy 144,000 is the number of people-12,000 from each of the 12 tribes of Israel-who are supposed to evangelize the world at the endtime.)
-Amazingly, the outside surface stones are cut within 0.01 (1/100th) inch of perfectly straight and at nearly perfect right angles for all six sides. And they were placed together with an intentional gap between them of 0.02 inch. Modern technology cannot place such 20-ton stones with greater accuracy than those in the Pyramid. Even more amazing is that the 0.02-inch gap was designed to allow space for glue to seal and hold the stones together. White cement that connected the casing stones and made them watertight is still intact and stronger than the blocks that it joins.
- We know from geometry that there is a universal relationship between the diameter of a circle and its circumference. Consider this: The height of the Pyramid's apex is 5,812.98 inches, and each side is 9,131 inches from corner to corner (in a straight line). If the circumference of the Pyramid is divided by twice its height (the diameter of a circle is twice the radius), the result is 3.14159, which just happens to be pi. Incredibly, this calculation is accurate to six digits. So the Pyramid is a square circle, and thus pi was designed into it 4,600 years ago. Pi is demonstrated many times throughout the Pyramid.
-Other numbers are also repeated throughout. Each of the Pyramids four walls, when measured as a straight line, are 9,131 inches, for a total of 36,524 inches. At first glance, this number may not seem significant, but move the decimal point over and you get 365.24. Modern science has shown us that the exact length of the solar year is 365.24 days.

This is a lot of information about the earth for human beings to know 4,600 years ago. But wait, it gets even more chilling:

-The average height of land above sea level (Miami being low and the Himalayas being high), as can be measured only by modern-day satellites and computers, happens to be 5,449 inches. That is the exact height of the Pyramid.
-All four sides of the Pyramid are very slightly and evenly bowed in, or concave. This effect, which cannot be detected by looking at the Pyramid from the ground, was discovered around 1940 by a pilot taking aerial photos to check certain measurements. As measured by today's laser instruments, all of these perfectly cut and intentionally bowed stone blocks duplicate exactly the curvature of the earth. The radius of this bow is equal to the radius of the Earth.

Apparently, the people that built the great pyramid knew a lot more information than the humans of 4,600 years ago. Does this mean that I'm implying the pyramids were built by aliens? Perhaps, but maybe not. It could have been some sort of spiritual or supernatural source too...

Taken from:

http://ds.dial.pipex.com/ritson/quest/orion/bauval.htm:

The pyramids have long fascinated Robert Bauval. He is Egyptian, born in Al-Iskandariyya (Alexandria) to Belgian parents, and has spent most of his life living and working in the Middle East. For many years he had pondered over the significance of Sah, the constellation of Orion, and its link to the pyramids. One night, while working in Saudi Arabia, he took his family and a friend's family up into the sand dunes of the Arabian desert for a camping expedition. Bauval knew that the seemingly inconsistent layout of the three Fourth Dynasty pyramids at Giza was no accident, and had applied his own engineer's mind, and those of many friends to the problem. Most agreed that the alignment, though unusual, was no accident, given the precise mathematical knowledge that the Egyptians had. His friend, a keen amateur astronomer, pointed out Orion, and mentioned, in passing, that Mintaka, the smaller more easterly of the stars making up Orion's belt was offset slightly from the others. Immediately Bauval saw the answer -- the three Belt Stars were aligned in exactly the same way as the three pyramids! Bauval checked the alignment in 2450 BCE by precessing the three Belt Stars back, and found that, due to their close proximity in space, great distance from Earth, and negligible proper motion, they looked exactly the same then as they do today. Of course, they had changed in declination -- then they were just below the celestial equator, at about -1 degree declination. The pyramids were a mirror image, the Earthly representation of the Belt of Orion, the destination of the dead King! The Egyptians were dualists -- everything they thought and believed was a duality. Everything had its counterpart, cause and effect, left and right, East and West, death and rebirth -- nothing was ever seen in isolation. They had constructed at Giza an exact replica of the Dual destination of the King. Far from being a tomb, the pyramid was the starting point of the King's journey back to the stars from whence he came, back to the First Time. Bauval initially made use of the astronomy program Skyglobe 3,5 for the PC. Though too inaccurate for serious work -- it does not take proper motion, nutation, refraction, for example, into account -- it was sufficient to clarify Bauval's mind as to the value of his discovery. Skyglobe 3,5 will plot the Milky Way on its charts if requested, and doing so added further proof to Bauval's theory. Giza is West of the Nile -- putting the plane of our galaxy into the equation showed that Orion is "West" of the Milky Way, in proportion to Giza and the Nile.