Great Pyramid's ancient mystery

It is the only one that still brings tourist money. None of the others have survived into the modern era.

How the largest and oldest Pyramid of the Giza plateau was built is still a mystery.

The Greek historian Herodotus said that it would have taken 30 years and 100,000 slaves to erect it.

Another theory is that it was built by peasants who were unable to work the land while the Nile flooded between July and November. They may have been paid with food for their labour.

What we do know is that it was built 4,500 years ago as a tomb for Khufu, a ruler also known as Cheops.

But robbers got to the tomb long before archaeologists did, taking with them any information about Khufu.

However judging from the sheer size of the Pyramid - which remained the tallest building in the world well into the 19th century - historians reckon he must have very powerful and very rich.

Security fears

Throughout their history, the pyramids of Giza have stimulated human imagination.

They have been to as "The Granaries of Joseph" and "The Mountains of Pharaoh".

Even Napoleon Bonaparte - not known for his modesty - felt humbled when he saw them during his conquest of Egypt in 1798.

"Soldiers!" the French general exclaimed. "From the top of these Pyramids, 40 centuries are looking at us."

Today, the pyramids and the Sphinx form the touristic region of the Giza Plateau near Cairo, and provide a welcome source of income for Egypt.

But recent instability in the Middle East has taken its toll on the site.

Last year the annual staging of Aida at Giza - a high point of Egypt's tourist season - was cancelled because of security concerns in the wake of the 11 September attacks.

The presentation of Giuseppe Verdi's opera, set in ancient Egypt, was due to feature more than 1,000 artists.