What are some theories on how the pyramids were built?

There are many theories regarding how the pyramids were built.

The most likely explanation is that a giant ramp snaked around the pyramid and this allowed the blocks to be rolled up the slope. Alternatively, some people believe that the blocks were raised using a lever system.

There are slightly more outlandish ideas which say that aliens brought cranes from space to lift the blocks, and recently, it has been suggested that the 2-ton blocks of stone were tied to kites and that the block were lifted in this manner.