Millions of people worldwide this year saw a live television broadcast which its promoters promised would solve a mystery about an ancient Egyptian pyramid. A small robot, Pyramid Rover, was inserted into a narrow shaft leading from the so-called “queen’s chamber” in the Great Pyramid at Giza. Viewers saw it run horizontally for a few metres and then begin to climb slowly upward, using its moveable treads to grip the roof and floor of the shaft. Nearly 65 metres from the shaft entrance it reached its goal: a small white stone slab with copper fittings, discovered blocking the end of the shaft by a similar robot in 1993.

Nine years of speculation ended when a camera mounted on the front of the robot was inserted into a pre-drilled hole and finally solved the mystery of what lay behind the 4,500 year-old door. The shaft ran a short distance further and was then blocked by another slab of white stone, this one more roughly finished, cracked and without metal fittings. No burial, no treasure, no papyri.

Presumably anticipating that a show billed as “Secret Chambers Revealed” might be viewed as an anticlimax if nothing was revealed after all, the organisers, Dr Zahi Hawass (general secretary of the Egyptian Supreme Council of Antiquities and in charge of all work on the Giza Plateau) and the National Geographic Channel, had prepared a distraction in the form of a stone sarcophagus, discovered recently by Dr Hawass’ team at Giza, which was opened live on the show while the robot was making its way up the shaft. Later it was announced that the robot would return to drill through the newly discovered slab next month, three months after the broadcast, in the hope of discovering what lies beyond.

The pyramid was built as a tomb for the Egyptian king Khufu (Cheops) in the mid-3rd millennium bc and is one of the greatest technological achievements of the ancient world. Originally 146 metres high, it is the largest of about 90 royal pyramids built between about 2700 and 1770 bc and, while it fits neatly within many of the general trends seen in pyramid design, in other ways it is unique. One of its unusual features is the complexity of the interior and it is because of this that interpreting the recently-explored shafts has proved so difficult - there are no parallels in other pyramids.

Most Egyptian pyramids have a small group of contiguous chambers below ground reached by a corridor descending from the pyramid’s north face. These chambers were usually built in a pit cut into the ground before the pyramidal superstructure was erected. However, Khufu’s pyramid has three separate chambers, one of which was excavated in the rock beneath ground level and remains unfinished, while the other two were constructed within the body of the superstructure. The burial chamber (usually referred to as the “king’s chamber”) was built more than 40 metres above ground level and is offset from the centre of the structure, while another chamber (misleadingly referred to as the “queen’s chamber”) is situated some distance below it.

Both the upper chambers have a pair of tiny shafts leading upward toward the exterior, one to the north face of the pyramid and one to the south in each case. The shafts from the burial chamber are now open at both ends, although this may not always have been the case. The queen’s chamber shafts were originally blocked at both ends and were discovered only in 1872 by the engineer Waynman Dixon who was searching for parallels for the burial chamber shafts. He investigated the shafts with the most advanced technology available at the time: metal rods which could be joined like a chimney-sweep’s pole and shoved up the shaft until they met an obstruction. Unfortunately, one of the rods got stuck in the northern shaft of the queen’s chamber which bends a number of times along its length; this hindered later investigation as it proved a significant obstacle to a small robot.

Given the technological achievement which the pyramid represents, it is appropriate that it is modern technology which is now allowing further investigation of it. Recent exploration of the shafts began in 1992 when German engineer Rudolf Ganten-brink designed and built the first of a series of robots small enough to climb the shafts as part of a project to ventilate the interior of the pyramid. The robots were appropriately named Upuaut (“the opener of the ways”) after the Egyptian jackal god who guided the dead to the afterlife.

Upuaut II, which was used to explore the queen’s chamber shafts, had long tracks for stability and to help it cope with the uneven floor of the shaft; and a retractable upper section which could be raised to grip the roof. Guidance by remote control was impossible because of the mass of stone between the robot and its handlers so a cable was attached to the back. Upuaut I and II carried cameras which allowed the insides of the shafts to be viewed for the first time in 4,500 years while the Rope Climber, a secondary robot which was attached to Upuaut II’s cable, carried equipment to measure the shafts accurately. On March 22, 1993, having navigated a number of obstacles, the robot made it to the top of the southern shaft and sent back the first extraordinary pictures of the beautifully worked stone and metal door.

Unfortunately, Gantenbrink fell out with the Egyptian authorities and was refused permission to continue his investigation. A new project was put together and was funded by National Geographic in return for broadcasting rights when the mystery of what lay behind the door was revealed. A new robot was built by the American company iRobot, based on Gantenbrink’s design but mounted with a drill designed to penetrate the limestone door. The drilling was done before the broadcast but only on the live show on September 17 was the camera inserted into the hole. To coincide with peak US viewing times, the broadcast took place in the middle of the night in Egypt and Europe and most of us had to wait until the morning when the block behind the original door was shown on breakfast news.

While popular interest has focused on what might lie behind the doors (treasure, Khufu, a statue, a papyrus roll with the secrets of a lost civilisation), specialists have inevitably been more cautious. Most considered it very unlikely that a chamber would be found. Such a chamber would have no entrance big enough for a person and would be vulnerable so close to the exterior of the pyramid. There has been considerable debate about whether the blockage found by Gantenbrink should even be described as a door; it has been variously called a portcullis, a plug, a slab and a block. There has, however, been considerable interest in how the exploration of the shafts and the discovery of the door influence our interpretation of the pyramid.

The day after its broadcast mission was accomplished, well away from television, the robot was inserted into the second queen’s chamber shaft which leads from the north wall, directly opposite the first shaft. This shaft was more difficult to navigate as it bends a number of times to bypass other passages in the pyramid and as a result had never been fully explored. Again the robot travelled for nearly 65 metres before the shaft was blocked by a door virtually identical to that in the southern shaft. Although this discovery was not as widely reported, it is an important additional clue to the purpose of these shafts.

The oldest and most pervasive shaft theory has been that they ventilated the burial chamber. According to this, the queen’s chamber was originally intended to be the burial chamber and was provided with shafts, but when the design was changed and work began on the king’s chamber, these shafts were abandoned and replaced by a new set of shafts in the chamber above. Although this theory still has its proponents, it is now widely viewed as untenable because, thanks to information collected by the robots, the shafts are known to run well above the level of the floor of the king’s chamber, suggesting they were not abandoned. The careful finishing and blocking of the shafts doesn’t seem to fit with their being abandoned. And no other pyramid was provided with ventilation so why should it have been necessary here? Architectural analysis also suggests that all three chambers form part of a single design.

A second theory interprets the shafts as passages by which the king’s soul could leave the pyramid to begin its journey to the sky. In later periods the Egyptians represented the soul or ba of a person as a human-headed bird which perhaps explains the scale of the shafts. Nor is the fact that at least some of the shafts were blocked a problem for this interpretation as the Egyptians often carved a stone false door in tombs to represent a point of communication between the world of the living and the realms of the dead. Solid stone was no barrier for a transfigured spirit. This theory is widely accepted among Egyptologists, although it does not explain why more than one shaft was necessary.

An extension of this idea, put forward by Egyptologist Alexander Badawy and astronomer Virginia Trimble in 1964 but based on decades of speculation, suggested that the shafts are oriented toward stars such as those of Orion’s Belt and a-Draconis which was the closest star to the celestial pole at that time. Computers allow us to calculate the position of the stars in antiquity and see which stars the shafts would have pointed at. Using Gantenbrink’s measurements, Belgian engineer Robert Bauval was able to update the work of Badawy, Trimble and others and revise the suggested target stars. The shafts are not straight and the stars would therefore not have been visible through them, but this does not preclude the idea that they were intended to direct the soul toward specific destinations.

A final set of theories relate the angles of the shafts to the geometry of the pyramid. Many of these theories are over-complex and bear little relation to the way in which the ancient Egyptians are likely to have thought about architecture. However, we do know that the Egyptians constructed the slopes of pyramids following a system of proportions which expressed the ratio between the vertical and horizontal in much the same way as we would talk about a 1 in 6 or 1:6 incline of a road. The angles of the shafts may have been constructed in such a way. Several researchers including Rudolf Gantenbrink, John Legon and Mary Brueck have pointed out that the angles of the shafts conform fairly closely to such ratios (1:1, 7:11 and 9:11; the latter angle is found in both of the queen’s chamber shafts). A numerical description of the angles, however, does not explain why the shafts were there in the first place.

The interpretation of the shafts remains controversial, although my own view is that the final three theories above are all correct. To me, directing the dead king’s soul toward specific stars (which were known to be important to the Egyptians) provides the best explanation for the number of shafts and the extraordinary amount of effort which went into constructing them, while the numerical proportions of the shaft inclines provide clues as to how they were built. If this is correct we can justify referring to the queen’s chamber shaft blockings as doors but we should not expect to find any secret chambers on the other side. The doors lead to something much more fascinating and mysterious: they are doors to the afterlife.

Exploration of the shafts illustrates well the advantages and limitations of modern technology in archaeology. If carefully directed, it can provide amazing insights but the problem of interpretation remains and technology is little help when it comes to the symbolic. Without the robots we would never have known of the doors and would not have been able to advance so far with interpreting the shafts. However, if you drill through a door to the afterlife all you are likely to reveal is a roughly tooled stone plug preventing debris from the pyramid core damaging the door itself. As with the wardrobe through which Lucy first travelled to Narnia, no amount of meticulous inspection is going to reveal its secrets.

While most Egyptologists think it unlikely that there will be a chamber at the end of the shaft, hidden chambers have been discovered before in Khufu’s pyramid.

Howard Vyse began to dynamite his way upwards from above the king’s chamber in 1837 (thankfully not a method of excavation considered acceptable today). It had long been known that there was a chamber directly above, but Vyse discovered four. Even in this case, however, the chambers did not reveal any treasure or lost esoteric wisdom: they were hidden not because they contained secrets but because they were functional, serving solely to redirect the weight of the stone above away from the ceiling of the king’s chamber and the body of the king below. No such reason exists for constructing a hidden chamber at the end of the queen’s chamber shaft. However, Vyse did find a number of painted graffiti on the walls of the relieving chambers. These were constructional notes and names of work teams, unseen since they were left by Khufu’s workmen 4,500 years ago, another fascinating clue to unravelling how the pyramid was constructed and by whom.

And so we must wait for the next stage in the unfolding drama of the pyramid shafts which we are told will take place next month when the newly revealed blocking is examined. What might lie behind the doors will continue to excite interest, regardless of how often the actual revelations disappoint. I think the new blocking revealed in September will turn out to be a thick stone plug inserted into the top of the shaft to protect the door below and that behind it will be the blocks of the pyramid’s core. Of course, I could be wrong.

Kate Spence trained as an architect before becoming an Egyptologist. She is a post-doctoral research fellow at the McDonald Institute and an affiliated lecturer in the faculty of Oriental Studies, Cambridge University