Here’s a hint - it’s BILLIONS and BILLIONS and BILLIONS…
From Live Science:
Even with cranes, helicopters, tractors and trucks at our disposal, it would be tough to construct the Great Pyramid of Giza today. Its construction 4,500 years ago is so astounding in some people's eyes that they invoke mystical or even alien involvement. But the current theory of the building of the Great Pyramid — the notion that it was assembled from the inside out, via a spiraling internal ramp — is probably still the best construction plan.
Following that plan, we could replicate the Wonder of the Ancient World for a cool $5 billion.
First, let's look at the blueprint: The pyramid is 756 feet long on each side, 481 feet high, and composed of 2.3 million stones weighing nearly 3 tons each for a total mass of 6.5 million tons. Legend has it that the structure was erected in just 20 years' time, meaning that a block had to have been moved into place about every 5 minutes of each day and night. That pace would have required the (slave) labor of thousands. While traditional theories hold that the pyramid was built via a long external ramp, such a ramp would have had to wind around for more than a mile to be shallow enough to drag stones up, and it would have had a stone volume twice that of the pyramid itself.
A new, more economical theory gaining traction among architects and Egyptologists holds that the bottom third of the pyramid's height wasconstructed by stones dragged up an external ramp. But above that — for the remaining 33 percent or so of the pyramidal volume — the Egyptians worked their way up through the inside of the structure, building around a gently sloping internal ramp and fitting stone blocks into place as they ascended. Furthermore, the workers could have re-used the stones quarried for the external ramp to build the pyramid's upper echelons, so that nothing went to waste.
Jean-Pierre Houdin, the French architect who developed the internal ramp theory, has collaborated with a team at Dassault Systems, a 3D graphics firm, to create a virtual model of the construction process (http://www.3ds.com/company/passion-for-innovation/the-projects/khufu-reborn/khufu-reborn). A team of scholars at Laval University in Quebec is now planning an infrared imaging investigation, which could soon reveal the spiraling ramp within the Great Pyramid; if found, it will be the final proof of Houdin's theory. But whether or not the theory bears out, Houdin says an inside-out construction would still be the best way to build the Great Pyramid.
"I am quite sure we could do the same today, and it would be the most economical method," Houdin told Life's Little Mysteries.
There would be two main differences between pyramid-building now and then. First, "Instead of people pulling the sleds that carry the stones up the ramps, you would use something with an engine," he said. Secondly, "for the [topmost] 10 or 15 meters, you would use a small crane."
Honestly, I wouldn't bet on today's builders to successfully recreate the Great Pyramids. Just look at the new buildings popping up; they don't hold a candle to ancient architecture in terms of longevity.
I suspect folks from way back knew a thing or two about construction that we've missed, and that's why their work still stands strong.
