It is obviously a very large complex of corridors under the valley and between all three pyramids. It takes a few kilometers:

The guide says: There are two mysteries:
1) how they did it that kept it for over 2000 years and did not collapse.
2) why did they do that?

In connection with the Great Pyramid, there is also talk of a large complex of corridors, which according to Zahi Hawasse does not exist. There is an obvious analogy.

Another interesting fact is that the corridors are covered with a mixture resembling concrete. It seems that after the corridors were dug, their surface was concreted.

Several megaliths were found in the tunnels. One of the megaliths is said to be created artificially and its surface resembles pottery.