There is a dictum in engineering endeavors that the techniques employed are reflective of technological feasibility, economic viability, and social motivations that avail themselves to the engineers and their labor force.
When structures are built routinely with megalithic construction (single cut blocks that begin to exceed 2 tons), then that has been done because these criteria could be satisfied, i.e., an engineer designs and builds with such blocks because the technology available for the act of construction makes it easy - in the sense of viability, economic cost, and social milieu.
The typical 2 ton block of the greater construction of the Giza pyramid, has been routinely demonstrated by various parties to be a size that could be comfortably dealt with - at least when handling for construction up to modest heights.
Such has not been so demonstrated for such interior blocks, though, that are, say, 200 tons. Technological handling techniques for a 2 ton block do not scale for use on a 200 ton object for the simple reason of the strength of materials problem. Ropes, wooden rollers, wooden levers, wooden crane facilities, level causeway road beds, etc., that were adequate for routine manipulation of 2 ton blocks do not similarly apply to 200 ton blocks.
The Baalbeck platform takes this matter to still yet another radical scale. Many of the blocks there are roughly 500 ton monstrosities, and then there are the 850 ton specimens placed at considerable elevation.
Modern efforts that go into the transport and handling of large objects, such as before mentioned nuclear reactor vessels, are considerable logistic undertakings. They press our technological capabilities using modern machinery to the limits. And here, in the case of the nuclear reactor vessel, we're still considerably under 500 tons.
The reason Baalbeck is built with such gargantuan megalithic construction is two fold:
*) The builders wanted to achieve a longevity for their construction that spans centuries - even thousands of years of endurance.
*) It was relatively easy for them to construct with 500 ton, 850 ton, or even 1200 ton monolithic blocks.
From an engineering perspective, that is the final determining factor - there must be eminent feasibility to achieve a particular manner of construction.
Modern archeologist and historians tend to have a single goal in mind when attempting to explain the presence of incredible works of megalithic construction that appear all around the globe (always of greater antiquity of the much inferior construction that appears in later periods). Their primary focus is to render an explanation that is couched in terms of how they conceived the peopling of the Earth to be in those remote times. Yet their explanations are never realistic with respect to the physical evidence that exist.
The level placement of blocks and surfaces is not so remarkable - as you say it's relatively easy to create a liquid level device. What is difficult is working large surfaces to level tolerances on all sides that it will be fitted adjacently to other blocks - particularly when that is in complex polygonal shapes (jigsaw puzzle style).
The clamping techniques you alluded to - well in both South America and Egypt the identical technique has been employed: Two adjacent blocks have something like an S shaped groove cut into them that spans the blocks. Then molten metal is poured into the groove.
The remarkable achievement here is the melting of this metal with some sort of portable foundry. All metal foundries discovered by archeology are set in place because of the significant construction required to provide fuel and air and then contain the high temperature heat with material that won't melt (ceramic materials/minerals). The problem being is that the molten metal can't be carried from some set permanent foundry to the point of application in the construction as it will cool too fast. The metal has to be made molten when it is in very close vicinity to the stone construction. This is where we get hand waving arguments that try to dismiss this dilemma - yet no one comes up with demonstrative verification of how it was done. In our advanced scientific age, this should be a simple matter, presumably. Yet when one is limited to the assumed technology available to those times, then it's not so simple.
Another case are vases found in Egypt with very long narrow necks which have been bore out with a drill like device. As the vase flairs out in size from the neck, then that too is bore out. No one has a clue how they had any capability to bore out these containers in this manner. Today we'd bore such hard minerals using ultrasonic drills. It's simply not a possibility using copper tools rotated by hand or minerals that are harder rotated by hand (even when employing leveraging devices such as draw strings and pulleys).
Of the explanations that the historians and archeologist put forth, none of the ideas have really been vetted by full, realistic replication of the proposed techniques. Usually these people advancing these explanations are by no means experts in engineering themselves. Occasionally a scientist will claim they have some manner of explanation for some aspect of what was achieved in ancient times, and yet again, no truly realistic vetting has been done to verify said explanation.
At one time a group of Japanese got permission to try and build a pyramid using stone quarried from like locales as the original pyramids. They started out trying to replicate the feat using approaches that they thought the Egyptians would have used - copper chisel tools, wedges, wooden levers, rollers, etc. They made almost no progress and then started resorting to modern tools and techniques. Even availing all that, they still ultimately had difficulty in engineering the structure of the pyramid itself and eventually abandoned the effort. It did not succeed in validating any presumed ancient technique of construction and instead left the entire matter as much of an enigma as its ever been.
When we look at Baalbeck, we see the Roman temple construction on top of the original megalithic platform does not employ the megalithic block approach. Instead the Roman construction is exactly the same technological style of construction that is found everywhere else throughout the Roman Empire. In other words the Romans didn't up and decide to go to one spot on the globe and for the first time build with 500 ton and 850 ton blocks. The Greeks and Romans, as high and esteemed as their civilizations rose to be, they have never evidenced the ability to engage in a manner of construction on par with the Baalbeck platform. The explanation is simple: the Greeks and Romans built in a manner compatible to their technological prowess, economic means, and societal milieu. They built in a manner that was easy for them to accomplish. Building with 500 ton and 850 ton blocks is not a feat their civilizations were capable of.
When we get to the Dark Ages we see remnant Roman civilization in Europe degrade considerably in terms of masonry construction. Once again it was the factors of technological ability, economic means, and social milieu. This did not see a turn about until the Knights Templars return from Jerusalem to France and then in France a revolution in construction appears over night.
The megalithic construction that appears all around the globe (including Pacific Islands) is the oldest construction, predating Greek and Roman civilization, etc., as civilizations that came later did not posses that technological prowess any longer. To this date no one knows how Baalbeck was built where 500 ton and 850 ton monoliths were moved from a quarry site to point of construction where there is no level causeway. It's a considerable mystery and no one has proffered a credible explanation that stands up against the scrutiny of engineering realities.
Today we'd use a steel rail bed that is underpinned by considerable non-compressible road bed construction to move objects 200 tons or more. If there is any knowledge of modern attempts to move single objects that are on the order of 850 tons, please post here as I'm very keen to know about such endeavors - as to what, from an engineering perspective, is involved.
The bottom line is an engineer is going to do what is readily feasible. If 500 ton and 850 ton blocks are routinely used, then that meant it was readily feasible to do so. If it was a Herculean effort (it pretty much would be today in the modern world) then what could conceivably justify using such large monoliths over, say, more facile 2 ton blocks? One answer to that is longevity of the construction. The Roman temple construction is about 80% deteriorated - yet the Baalbeck megalithic block platform construction is entirely still there. The builders seem to have put a great premium on creating structures that can last un-phased for thousands of years. It's fair to say from an historical perspective, it is only these ancient megalithic constructors that have had such a goal. The technological and economic factors of all subsequent civilizations have been such that they have not seriously rivaled the longevity standards of the megalithic builders. Why were the megalithic builders, as a class of people, so unique in this regard? Why did they have such unique standards and goals?
Modern archeologist and historians are consumed so much with their ridiculous hand waving dismissals of the truly puzzling implications of these ancient achievements that they never get around to trying to fathom the still deeper issues that exist here. They'd rather spend their time trying to deride the geological science of Robert Schoch -
Hour 1 - The Mystery of the Sphinx The Egyptologist would actually suggest their opinions and suppositions should be elevated in priority over evidences coming from hard physical science (and affirmed by Schoch's peers)!
