The Great Pyramid is not just filled with rubble. Neither are the other pyramids alongside it on the Giza Plateau, nor the slightly older pyramids further south at Saqqara and Dashur.

It’s not at all unreasonable to suspect that, though, as it would have made building them much easier. But when you’re there in person you can actually see evidence of the structure, style, and substance of the interior blocks of the pyramids too in various ways.

First, explorers, rulers, and and other curious or greedy characters over the millennia have hacked into the sides of several pyramids, including the Great Pyramid. In fact, the current entrance to the Great Pyramid for visitors today isn’t the original entrance. It’s an opening that was bored into the monument in more “modern” times to access the interior pᴀssageways and chambers, and those tunnels had to go through through solid stone, not rubble, as you can see when you enter this “newer” entrance.

Second, when you’re in the pᴀssageways and interior chambers, you can look up and see the solid blocks above and around you when you’re smack dab in the middle of the monument. Of course you could say that maybe they made the walls surrounding the interior chambers out of solid stones along with the exterior walls, but I think the first point above showed how that theory can be proven wrong from all the boring, tunneling, and hacking of new openings and tunnels that occurred much later and which found solid stone the entire way through.

Lastly, while not necessarily the case with the Great Pyramid, you can see more solid interior stones in some of the older Pyramids that haven’t held up as well and have crumbled more than 1 or 2 layers deep. This can even be seen at Giza if you look at the Queens Pyramids beside the Pyramids of Khufu (the Great one) and Menkaure. Some of the Queens Pyramids are eroded almost completely away such that you full view of the interiors of those that were solid stone too.

Only 719 years ago, the Great Pyramid was still covered with very accurately laid white limestone except for a forced pᴀssageway made in 820AD by a Muslim Prince and his men looking for treasure. In 1303 a great earthquake struck the Cairo area and much of the limestone surface was dislodged. For about 200 years it was used as a free source of fine limestone, like a rock quarry. The entire 13-acre surface of white limestone was sadly carried away and used for construction projects in the city. Many of these buildings still exist.

For hundreds of years after the earthquake no one paid much attention to the Great Pyramid and sand and rubble covered the base up to as much as 25 feet/10 Meters in height, so a few of the original casings stones were fortunately preserved.

If it were not for the sand and rubble that was around the base of the Great Pyramid these original casing stones would not be as well preserved as they were. From these few original casing stones surveyors have been able to determine the dimensions and angle of the very accurate outer covering over the entire structure.

In the mid 1800’s there was more historical and scientific interest in the structure so the sand and dirt was removed.

When I visited the Cairo and toured the Great Pyramid, I became frustrated with the Egyptian Hawkers continually approached tourist to sell them trinkets. They were very aggressive multi-lingual sales professionals, to put it kindly. After entering the Pyramid one day to see the Grand Galley, the King’s and Queen’s Chambers so called, the next day I returned alone to just walk around the perimeter and contemplate where I was and what this amazing structure is. But everywhere I went the Hawkers followed trying to sell something. I climbed up a few levels to just get away from them and sit and meditate. To my amazement I saw many small pieces of white limestone still all over the structure from the time that larger sections of limestone were removed for building projects. There must be thousands of small pieces of limestone still there.

To answer the question, the base of the Great Pyramid was covered with sand and rubble for centuries, but for the last 200 years this has been removed and you can see the original base, sockets and a few of the original casing stones.