What is certain is that whoever built it was of a civilization more advanced than the earth's present one.

That's incorrect. We know that they didn't need advanced technology. They were built with ancient technology: levers, rollers, copper (and later bronze) tools, and lots of muscle. But not as much as you might think. Even the Great Pyramid of Giza could have been built in less than ten years with a relatively small workforce of 5,000 full time workers and a few tens of thousands of part-time workers.

And no, the majority of workers were not slaves. Many were skilled tradesmen, and even the laborers were free men, either working for wages or providing labour in lieu of taxes. Sometimes they even went on strike.

The pyramids of Egypt and Kush (modern day northern Sudan) were built over a period of 2000 years, and we can see the evolution of pyramid technology from mere dirt burial mounds to the outstanding work of engineering that is the Great Pyramid of Giza. Before the pyramids, kings were buried in stone mastabas, rectangular stone buildings that are much easier to construct. From there they developed step pyramids, before the invention of the pyramid shape we know today.

We can see their engineering mistakes: the Bent Pyramid was too steep to be stable, so halfway up they had to reduce the angle of the walls to stop it collapsing. The older pyramids were made of solid stone, but the younger ones are cheaper, using mudbrick for the internal construction and stone only for the outside.

Only the outside stones were cut carefully to fit together neatly. Inside stones were rough-cut, and the gaps filled with rubble and mortar. There is also some evidence that some of the blocks may even have been a form of artificial concrete-like stone, although most archeologists doubt this.

As far as the construction methods go, modern experiments prove that a small pyramid 6 metres high can be constructed in under a month using only 60 or so workers. Some shortcuts were used but the stones were carved and placed my muscle power and hand-tools alone, no electricity or modern technology needed. The blocks of stone used were 2.2 tonnes each. Just 12-20 men can tow a 2 tonne stone block. Other experiments show that just 45 men can move a 16 tonne block of stone on rollers.

As far as transport goes, when the pyramids were built, the Nile river was higher and there was a now dried out branch of the river that went to the Giza area. Transporting stone on water barges is easy with 4000 year old technology.

Its only soft, privileged modern-day weaklings who think that the pyramids had to be made using advanced technology. People in the past had no problem with using lots of muscle power and hard yakka in construction.