Most Egyptologists contend that the pyramid collapsed at some time after it was finished, and this is supported by the fact that a large funerary complex was added to the site. There is no evidence that the pyramid collapsed while under construction, as some suggest.

In theory, it was a spectacular collapse — a few of the tightly packed, angled facing stones were sqished out on the side…and in a cascade of stone, the facing collapsed, an avalanche of limestone and loosely stacked filler blocks.

The core that remains is unnaturaly smooth and is actually the facing stone that was added when the pyramid was turned into an eight-step pyramid. It supports the idea that Maidum was like a ‘nested set” of pyramids one completely finished face hidden inside a larger outer shell.

Even on the remaining tower, gaps in the limestone facing reveal the haphazard way that the inner stones were used for fill. Most likely, the loose, rubble-like interior was unable to support the additional weight, and kablam! it slid down in a heap. The actual cause is unknown, but theories abound (including an interesting dissertation on fluid dynamics and the shape of the rubble hill) on how it collapsed. It is also suggested that the collapse of Madium prompted the change in angles of the Bent Pyramid in Dashur.