In Cambodia, in Angkor, there is an ancient reservoir called the Western Barai (barai is an artificially created Khmer reservoir and there are several of them).
West Baray is the largest reservoir in Angkor and, as far as I remember, one of the largest ancient ones in the world.
The most important thing is the perfect rectangular shape. If not for the form, it seems to me that everything would be easier to explain. The reservoir is 8 kilometers long, slightly more than 2 kilometers wide, and the depth is almost everywhere - 5 meters.
I don't know how, but the creation of the reservoir was attributed to the very beginning of the 11th century, and the end to the middle of the 11th century. Construction began under one ruler, and ended under another. The purpose of these reservoirs is, of course, unknown.
This is where all the official information ends and I want to speculate. To begin with, the most important question is the rectangular shape.
In what way did the ancient people mark out a rectangle 8 kilometers long? Moreover, it is perfect, modern images from above are impressive, to put it mildly.
Promotional video:
Let's imagine that one official version, which is suitable for absolutely all cases, is a lot of people and long work. But according to the official version, such a reservoir was built from 50 to 60 years, and maybe less.
But is it possible to make a reservoir of this size and such depth in 50-60 years by manual labor? The answer is obvious, considering that Cambodia is, in principle, a fairly small state, although it is located in Asia. And what population there could have been about 1,000 years ago?
This is not to mention the age itself. It was not the age itself that was determined, but at the time of what rulers the West Barai was allegedly created, but how is this explained, as proved? Unknown.
Well, the most important question, as it seems to me, is where did the soil disappear? Just imagine how much soil has to be left after a "hand" excavated reservoir with a depth of 5 meters and a length of 8 kilometers. But as you might guess, nothing was found, all traces simply disappeared.
Have all the tons of stones and earth that should have remained on the shores of this reservoir "evaporated" in 1,000 years?
The question of the absence of residues after the creation of the reservoir confuses the official version and it is unlikely that anyone can explain this fact. But going further, what is the purpose of the object?
I've read about several versions. The first and commonplace - this is really a reservoir, only obviously, not created by hand. That is, an unknown civilization could also create reservoirs for its own needs, it is foolish to deny it right away.
The second version is something else. In other words, before the "reservoir" was filled with water, there could have been something there. Although West Baray was kind of investigated, maybe not in detail, but still.
And the latest version is the quarry. The version sounds quite plausible, since the rock could be mined, forming a rectangular shape, which has already been filled with rainwater.
In any case, the fact is only that the official version of this reservoir is impossible purely theoretically, since Cambodia did not have enough population to create this object in 50 years. For manual labor there, at least hundreds of years are needed, and that is far from the fact that everything will turn out perfectly.
Maybe, of course, some will again explain the creation of a reservoir by the fact that all the peoples of Asia have come together to create a reservoir, abandoning absolutely everything. We did not sleep, did not eat, in 50 years everything was built, tons of soil were taken out on something, far away, so that it would not be found and that's it.
So the official version would not sound bad, but the ancient reservoir, in principle, is not particularly explained, and scientists are not interested in it either.
You can end there. In principle, one can guess for a long time about the creation and purpose of an object, but it is impossible to create it by manual labor in such a period of time and this is a fact.