There are seven wonders of the world today and the pyramids of Egypt are often on the top of the list. This is in part due to their age as well as the mystery that surrounds how and why they were built.

Here are 13 Facts on the Egyptian Pyramids You Might Not Know.

The Great Pyramid of Giza has a swivel door at the entrance that weighs about 20 tons. It could be easily pushed open from the inside but on the outside, it was very difficult to find because it fit perfectly with the structure. There are three of these swivel door entrances.

The Great Pyramid of Egypt is the oldest of all Seven Wonders of the World.

The Pyramid of Khufu is the oldest and the largest Egyptian Pyramid. It is as high as 481 feet. Archaeologists believed that it was the tallest structure in the world for about 3800 years.

The Great Pyramid of Giza was constructed around 2500 B.C in almost 20 years.

Inside the Pyramid, the descending passage is pointed toward the star Alpha Draconis. It is said that there is no other star that has aligned with the passage since then.

The Pyramids were not built by Slaves. They were built by 100,000 highly skilled and trained laborers who were paid for their time. Indeed, at the time it seems like skilled workers were keen to be involved in the project.

Within the Giza Necropolis, there are three Pyramids and the greatest of them is the Pyramid of Khufu.

It is estimated that it took 23 years to complete the building of the great pyramid of Giza. Other pyramids were being built simultaneously and also took about this length of time according to historians.

The weight of the Pyramid is estimated as 5 million 955 thousand tons.

It is estimated that 2 million 300 thousand stone blocks make up this pyramid. Those blocks weigh from about 2 to 30 tons The heaviest block weighs just about 50 tons. That is heavier than an elephant.

The machinery that was used to build the Great Pyramid of Giza cannot be reproduced today, even though it has been analyzed by the engineers but they still can’t make it.

The mortar which holds the blocks in place has lasted over four and a half centuries. The mortar has been analyzed extensively by scientists but they still can’t work out its composition.

The Sphinx was the first royal statue in Egypt. It is said that the sphinx was created from limestone and was built with the pyramid of Khafre. The statue represents power with a lion body and human head.