For more than 4000 years, the pyramids of Giza have towered over the west bank of the Nile just south of Cairo, Egypt, sparking innumerable theories on everything from their construction methods to their astrological connections. Here are 12 facts about the largest of them all, the Great Pyramid.

1. THE EARLIEST PYRAMIDS IN EGYPT WERE BUILT A CENTURY PRIOR.

Tombs for the kings of Egypt had been constructed underground for many years before the pharaoh Djoser built a step pyramid in Saqqara, south of Giza, around 2630 BCE. Djoser’s tomb predates that of Sneferu, whose Red Pyramid was the first completed true pyramid, built sometime between 2613 and 2589 BCE.

2. THE GREAT PYRAMID WAS CONSTRUCTED BETWEEN 2560 and 2540 BCE.

Not long after Sneferu’s 341-foot tall Red Pyramid was completed in Dahshur (his first pyramid in Maidum was abandoned, and his second was turned into the Bent Pyramid), Khufu began work on the Great Pyramid at Giza. The largest of all the tombs built in the ancient world, the Great Pyramid is the centerpiece of a complex that includes tombs for Khufu’s wives, a mortuary temple, valley temple, boat pits, and a causeway.

3. THE GREAT PYRAMID WAS BUILT FOR THE PHARAOH KHUFU.

The second pharaoh of the 4th Dynasty, Khufu, Hellenized as Cheops, was the son of Sneferu and Hetepheres I and likely ascended to the throne in his 20s. Very little information about Khufu has been preserved, and the conflicting accounts of his reign were written centuries after his death, most notably in Herodotus’ Histories. The only acknowledged statue of him stands a mere three inches.

4. IT WAS THE TALLEST MAN-MADE STRUCTURE IN THE WORLD FOR THOUSANDS OF YEARS...

At 481 feet tall, the Great Pyramid eclipsed every structure ever built until the completion of the Lincoln Cathedral in 1311 CE. The Cathedral topped out around 525 feet before the collapse of its central spire in 1548.

5. ...BUT IT HAS SHRUNK BY ABOUT 25 FEET.

Today, the Great Pyramid stands only about 455 feet tall, as four millennia of erosion has sliced 25 feet of stone from the structure. An iron triangle currently sits atop the pyramid and represents the pyramidion, or capstone, that once marked the apex of the structure.

6. ABOUT 2.3 MILLION STONE BLOCKS WERE USED TO BUILD THE PYRAMID.

The quarry at Aswan, about 525 miles upriver, was the site for the stone used to make the massive blocks that comprise the pyramid. Each block weighs about 2.5 tons on average, and the pyramid itself is estimated to weigh 6.5 million tons.

7. A SERIES OF RAMPS WAS LIKELY BUILT TO CONSTRUCT THE PYRAMID.

With no hard evidence, historians and scholars have theorized that a system of ramps had to have been the method for raising and maneuvering the massive granite blocks for the Great Pyramid. Archaeological evidence at other pyramid sites indicates that linear, staircase, and spiral ramps were used to slowly bring stones hundreds of feet into the air. Once there, historians believe wooden and bronze levers were used to intricately position the stones.

8. THE INTERIOR CONTAINS THREE CHAMBERS.

Designed as a tomb, the Great Pyramid contains three burial chambers that were intended to house Khufu and the litany of goods and treasures he would take with him in the afterlife. Upon entering the pyramid, a passage (3.1 feet high, 3.4 feet wide) descends about 354 feet into the bedrock, levels off, and continues another 29 feet to an unfinished, underground chamber. About 93 feet down the descending passage, a hole in the roof leads to the ascending passage, a 129-foot stretch that rises to the Grand Gallery (it is the only known pyramid with a passage that slopes upward). At the start of the Gallery is a passage to the Queen’s Chamber, which measures 18.9 feet by 17.2 feet and is 20 feet high. A series of shafts, extending from the north and south walls, were explored multiple times but their purpose has yet to be uncovered.

Back at the Grand Gallery, a 28-foot high, 153-foot long passage leads up to the King’s Chamber. Inside, the walls are entirely covered in granite, and a pair of shafts, which at one point were thought to be air shafts, slope up and out the north and south sides of the pyramid, leading many experts to believe that they had an astrological purpose. Khufu’s sarcophagus is the only object that remains in the room, and its lid is gone and a chunk of the corner is missing. Atop the roof was a series of relief chambers that took pressure off the room below.

9. ALMOST EVERYTHING IN THE CHAMBERS HAS BEEN TAKEN.

Some accounts state human remains were present in the King’s Chamber around the 9th century CE, but constant looting has left the interior barren except for Khufu’s red-granite sarcophagus. In addition, the white limestone casing that once covered the exterior was also taken and used by various rulers and kings in other building projects.

10. HISTORIANS BELIEVE SKILLED LABORERS BUILT THE PYRAMID.

Long thought to have been the work of thousands of slaves, experts today believe 20,000-30,000 skilled laborers, including stone masons, engineers, architects, surveyors, builders, and other craftsmen, were conscripted to construct Khufu’s temple. Egyptologists Mark Lehner and Zahi Hawaas theorize that a small crew worked year-round on the project, while a larger collection of workers was summoned during the summer months when the Nile flooded the surrounding valley and integrated with the permanent labor force.

11. KHUFU'S SON AND GRANDSON BUILT PYRAMIDS ON THE SAME SITE.

Along with his tomb, Khufu’s pyramid complex includes three small pyramids built for his wives, a mortuary temple, and mastabas (tombs) for the relatives and officials who would accompany Khufu on his journey in the afterlife. His son, Khafre, built a 446-foot pyramid, which appears taller than Khufu’s from certain angles because of its position on slightly elevated ground. Khafre also commissioned the the Great Sphinx at the front of the complex. Menkaure, the son of Khafre and grandson of Khufu, built a relatively modest 213-foot pyramid nearby.

12. IT IS BOTH THE OLDEST AND THE ONLY REMAINING ANCIENT WONDER.

Named one of the Seven Wonders of the Ancient World, the Great Pyramid is the only work that has survived into modernity. Archaeological evidence has been discovered that indicates, like the Great Pyramid, some of the legendary structures (the Lighthouse of Alexandria, the Mausoleum at Halicarnassus, the Temple of Artemis at Ephesus) were real, while the others (the Hanging Gardens of Babylon, the Statue of Zeus at Olympia, the Colossus of Rhodes) are harder to verify, and may be composites of legend, myth, and fact.