[Continue to three more today, what is best not to have three more before the shelf, to save the manuscript and the like, it doesn't matter for the time being, how much more or less, it can be regarded as a workout for the update on the shelves in the future. I'd like to try to do it for a few days, can you support me?]

When everyone heard what Lao Niu said, they were shocked.

I just feel that there are too many unknown secrets in this deep mountain.

Previously, it was said that there must be karst caves in karst terrain under the large underground of this mountain, as well as various spaces connected to the caves.

But now it is found that the scope of this space radiates at least 70,000 or 80,000 square meters. Such a large space area is unheard of, but what is even more shocking is that there are obvious traces of man-made underneath.

Steel, concrete. This is a trace that only appears in places where there is a large amount of traffic.

Suddenly, the pupils in Li Xun's eyes shrank, and he muttered in a deep voice: "Xu Dingshan told me before he died, this is Dragon City. Isn't it really a city down here? ”

"Dragon City?"

"Yes, Xu Dingshan said it, and threatened us, saying that they are all people of Dragon City. ”

"Is this really the Dragon City down here?"

"It's getting more and more confusing, and I can't figure out how there can be a city down there. ”

"Where did the reinforced concrete come from?"

“……”

Lao Niu became excited: "If a city is really built at a depth of two hundred meters underground, what a ingenious work this designer must be." ”

Expert Xu smiled: "It's not difficult to ......"

"Why isn't it difficult, maybe you don't know architecture. Professor Niu interrupted.

"There is ground pressure for 200 meters underground, and once the internal space is too large, the soil layer above may collapse at any time. And concrete isn't really suitable for underground, you're talking about the mines, right? They don't use concrete, it's all planks and steel pillars. They can only dig tunnels underground, but they don't dare to open up such spaces at all. With such a large space, the difficulty is extremely huge. ”

Expert Xu was stunned: "Is it difficult?"

Lao Niu nodded seriously: "It's difficult, it's very difficult." The hardest part is not really to build, but how they make sure that they don't collapse. Opening up space at a depth of 200 meters underground is a completely different concept from digging a tunnel. If you think about it, those mines, just drilling holes in the ground will collapse. And this is to hollow out the ground and dig out a space, what a big project it must be, and it will not collapse, what kind of means is this? ”

Expert Xu was speechless, he really didn't understand the doorway.

Li Xun frowned and said, "There should be a cave down here." Professor Niu, if you want to say that someone can carve out a space of tens of thousands of square meters at a depth of 200 meters underground, this is unrealistic in itself. This kind of engineering volume cannot be completed without more than ten years. But if the cave below is naturally formed, then it is not too difficult. ”

The cow expert was stunned, and smiled a little hindsightly: "It's the same." ”

“……”

Then, the group followed behind the cow expert, who pushed the ground penetrating radar forward in an attempt to find the entrance to the cave.

But as they probed more and more, they discovered more and more how huge the space below was.

Until the entire underground space was explored, Lao Niu came up with a data - 200,000 square meters.

It's almost the size of a small town.

And such a large area of space appears underground.

It's a dungeon, and that's not wrong at all.

However, the old cow can only calculate its area, but not the volume of this space. When the probe mine reaches the hole below, the radiation range is almost at its limit, and it is difficult to reflect back after entering the air, so the depth of the hole cannot be detected.

If you don't know the depth of the space, you don't know how high the ground to the top wall of the space is, and if you don't know this, you can't calculate how many cubic meters it has. Without the conclusion of cubic meters, it is impossible to calculate the oxygen content in this space, as well as the various indices.

The data is not clear, which affects the preparation and follow-up actions in the early stage, because it is unknown, there is no way to get too much information, and there is no bottom in my heart.

Avoiding these, the strange thing is that no matter how the old cow looks, he can't even find where the entrance is. There's a space down there, but strangely there's no passage on the ground that leads to it.

According to common sense, there should be a karst cave or cave below, and then connect to the water cave under the Longtan River.

But this cave was not found, only the space could be found.

The old cow stopped, gave up, and said with a serious face: "I haven't found the hole yet, so there is only one explanation." ”

Li Xun asked curiously, "What?"

"This cave, probably deeper underground, is under space. If this underground space is compared to a city, the hole may be the sewer manhole cover on the ground of the city. And the cave is very likely to pass through under the space. This is very likely, and this is the strange thing about karst landscapes, which can happen in all kinds of terrain. ”

Li Xun frowned and said, "And then?"

Lao Niu clapped his hands: "No more, unfortunately, the depth of the ground penetrating radar has reached the limit." After penetrating 200 meters of soil into the ground, the signal was almost faint, and I could hardly find any other clues. ”

Li Xun said with a smile: "Your statement is wrong, there will definitely be a hole on the surface to enter." ”

"Why?"

"Because you said that there is reinforced concrete material underneath, that alone means that there must be an entrance to the surface. It's impossible for reinforced concrete to go down more than 70 meters through that water hole and then dive all the way down to the bottom, right?"

Lao Niu glanced at Li Xun and was suddenly startled: "Yes, that's the truth, but where is the entrance to the cave?"

Li Xun thought for a moment, and then suddenly smiled: "Since I haven't found it after talking about it for so long." Then we should think where we are most unlikely, where we ignore. ”

"What did we overlook?"

The old cow asked.

Li Xun pointed to the hill of the manor where he slept last night: "We haven't visited that place, have we?"

"But that's where we started. ”

"No, we took the GPR and left the manor for hundreds of meters before we started to explore. ”

Li Xun said: "Your radar radiation range is seven or eight thousand square meters. The length of the vertical and horizontal lengths is actually about 100 meters. We walked more than a hundred meters to start probing, and the manor, the entire fence was more than a hundred meters. The area of that manor occupies half of the mountain. ”

The cow expert suddenly woke up: "Yes, it is possible that it is indeed in the manor." It is highly likely that the manor is a cover-up. Go, go back. ”

The old cow took the lead and began to walk back, and everyone hurriedly followed. They believed Li Xun's words more.

In fact, Li Xun believes in his nose more.

I still remember the first time I first came here, I found the smell of a big snake in the corner of the manor......