The Bent Pyramid is weird. Ignoring its dual slope for a moment, the Bent Pyramid has features that no other pyramid has.

So there's this pop culture idea that the pyramids used camouflage as a security method: That the pharaoh and his grave goods would be interred inside, and then the passageways plugged up and hidden so they'd look like any other stone on the monument. This doesn't seem to be the case; all pyramids have an entrance roughly centered relatively low on the North face. Those with entrances that have intact casing stones have big, showy lintel blocks above the entrance that would make a plugged entrance easy to find. There is no evidence that a pyramid entrance was ever concealed.

...Except on the Bent pyramid. Which does have a fairly obvious entrance low on the North face, but also has a hidden side door high on the West face. This entrance was hidden by an ordinary looking casing stone and was only discovered and opened in 1951. When that entrance was concealed, Thuban was the North star, not Polaris. It was opened during the fifth season of Howdy Doody.

Unlike every other known pyramid, the Bent pyramid was apparently built with two unconnected interiors. The standard North entrance leads to the typical descending passage that descends through the superstructure into the bedrock below, levels out. From there it opens into a high corbeled chamber. A passage high on the wall of this chamber leads to another high corbeled chamber; a modern wooden staircase allows access up to this chamber, which has a bizarre vertical shaft off to one side commonly called the "chimney." This is centered under the pyramid's apex and has some odd architecture, it's one of the most inexplicable pyramid features I'm aware of.

As originally built, this would have been the end. There's nowhere else to go. At some point in antiquity, there was a passage carved through the masonry high in this upper chamber, which leads almost directly to a horizontal passage running East-West. To the west, past a pit trap, is one of the pyramid's two portcullises. Many pyramids feature portcullis stones (or the remains thereof) but the Bent pyramid's are the coolest. They close across the passageway diagonally, so that no edge of the stone is flush with any surface of the passage, making it lever proof and impossible to open once closed. The Western one was sealed, but has since been tunneled through. The floor before the portcullis has also been excavated, in an apparent attempt to undermine it. Beyond is an ascending corridor that leads out to the casing stones.

To the East is a similar portcullis that closes the opposite way (one from the North, the other from the South--good thinking, Imhotep) but this one has never been closed. To this day it's still propped open by an ancient cedar log. Beyond is the apparent burial chamber, which had a now-destroyed false floor.

It seems like the pyramid was designed with an upper burial chamber designed to be secured behind portcullises, traps and a concealed entrance, with a separate and unconnected chapel below entered from the North for worshippers.

The popular story is that the Bent pyramid was a fuckup, and then the nearby apparently superior Red pyramid was built. Except the Red pyramid doesn't have a satellite pyramid or a temple complex. Sneferu's cult was still active 1000 years later, and they practiced at the Bent pyramid. So even though no sarcophagus has ever been found, there's evidence to suggest Sneferu was actually buried in the Bent pyramid.