Take the Temple of Karnak , in Egypt. This structure consists of an array of columns, which support stone mintel blocks…some of them weigh 10 tons! As far as I know, the ancients did not have cranes (a late medieval invention), or ropes capable of handling such weights. Yet these blocks were placed with great precision, atop 75 foor high columns.
Did they backfill the entire structure with sand and haul them up a ramp?
Or were they jacked up by giant levers?
I was always fascinated by thefact that the Egyptians and Greeks NEVER invented the arch…so their columns always had to be close together.
In my opinion, the Romans were the best engineers of the ancient world. 
Many theories will be presented, and while this is fodder for Great Deabtes, please consider this:
Try to change the typical time frame reference you have. Imagine you were given the following goal: “In 15 years, raise five 8 ton slabs to the top of…”
I have heard everything to the power of wind, water, men, aliens, etc. When constructing a solution, or wrapping your brain around one, think about the time permitted.
Not my area of expertise, but from my readings ramping has been the most widely accepted explanation.
Ramping is widely accepted, and so is the construction of simple scaffolding. Just place two wooden beams under a block. Then use a wedge to lift the block high enough to place another two beams under it at right angles to the first. Repeat this process and you can lift the block to almost any conceivable height easily and rapidly.
You wouldn’t need 15 years to do it, a week or two at most for skilled labourers.
The rectangular structure of two beams crossing two below to the desire height is known as ‘cribbing.’ The height is limited by the length of the beams for reasons of stability.
Another theory is that the entire structure was filled with sand as the walls and collumns were stacked. Finally the lintels and top members were put in place and the sand removed.