an external ramp that wrapped around the outside of the smooth limestone cased pyramid?
a single elevation ramp of 1.5 kilometers for the placement of the highest blocks?
the fifty degree ramp we know as the entrance slope to the King's Chamber?
All the above considerations come under the title, "Supposed methods of construction of the Great Pyramid of Khufu just outside Cairo in Egypt." For ten years, French architect Jean Pierre Houdin has been obsessed with this puzzle.
His intriguing answer? AN INTERNAL RAMP that spiralled up the pyramid at an angle of seven degrees that allowed the mathematically accurate smooth outer limestone blocks of the once-white pyramid to be placed FIRST and the rougher support blocks (that we see today because of decades of spoliation of the outer limestone casing) to be added as filler as the build progressed, layer by later.
Houdin even applies an ingenious counter-balanced function to the King's Chamber slope, beyond any supposed fanciful or ritualistic design considerations of the pyramid builders, that minimises the supposed six hundred press-ganged slaves pulling sixty tonne granite blocks into place to a much more managable one hundred dedicated workers.