Researchers drilled through the block at the end of the shaft in 2002 and indeed found an honest-to-goodness secret chamber. Treasure hunting wise, though, it was the most disappointing Easter egg in the history of ransacking cultural landmarks -- it boasted some ancient red graffiti, a dummy door and absolutely nothing worth stealing whatsoever.
However, the other secret chamber is a different matter. There's another secret passageway behind the king's burial chamber, and this one is big enough for a man to go through:
Not much of a man, but still.
Those four stones in the center are carefully placed in a zigzag pattern to take the load of the stones above off them. Experts are fairly certain there are hidden chambers behind this portico structure, and radar probing seems to back this up.
What's more, what we currently think of as the King's Chamber of the pyramid might have been just a dummy, and that hidden room may be the actual inner sanctum. Who knows what riches it might contain?
According to this inscription, armless stick figures.