In the dark cave, the sound of water drips.

This is the third time that Lu Yuan and Su Mei have come to this cave. In a sense, they are really familiar with the road.

And after three experiments on destroying caves, we all know how unscientific and evil this cave is.

Although Roland was able to survive alone for more than ten years by relying on this cave, most of the reasons for his acquisition of the legacy left by all the expedition teams, it also shows that at least the conventional danger of this cave is not that great.

So what exactly caused the Roland Expedition to destroy it?

So the mystery points to the mysterious bronze door without a doubt.

And now, Lu Yuan and Su Mei need to explore this bronze door.

It is purely a lie to say that there is no anxiety in my heart.

What humans fear the most is always the unknown.

Because unknown means uncertainty and uncontrollable.

"I want to know what you are thinking now?" Lu Yuan said to Su Mei, and there was a meaning of lively atmosphere.

"I'm thinking now, I'm very happy to be with you?" Su Mei smiled and said.

"Why do you think this way?" Lu Yuan asked.

"Because I'm scared." The girl's laughter was crisp.

"And I know, you may be scared, too."

"Two people who are very scared can encourage each other and become less afraid."

"Or, no matter what is ahead?"

“We should all have the determination and courage to face it.”

...

...

The 500-meter-deep cave has a real distance of about three kilometers to reach the deepest point.

Although the air here is dirty and hot, it does not have much impact on Lu Yuansu Mei and others wearing Doomsday Mecha. Even this rugged and steep journey is a bit of ambiguous for Doomsday Mecha.

The only thing worth noting, or the only thing worth noting is.

In normal caves, they will not be so deep, almost close to the gates of hell.

Although the crust and mantle in the center of the earth may be as thick as 6,000 kilometers, these 500 meters are really a big deal for them.

But for humans, such depth is already very anti-human.

Or, usually a large pit that is dozens of meters and one hundred meters gives people the feeling of a bottomless abyss. It is 500 meters deep here but does not penetrate the water layer of the groundwater. It is very magical and unexpected.

And along the way, the passage in this cave has always been able to easily pass at least one Doomsday mecha. In other words, the height of the cave has always been more than five meters. This height cannot be said to be dug by Roland's expedition team for the convenience of entry. This completely violates the general cave tunnels that are tortuous and deep, and are of varying thickness.

"I feel very strange." They have arrived at the deepest part of the cave, which is an underground platform centered on a huge hot spring. You can see that under the light, the hot spring is gurgling outward and releases a large number of bubbles. These scorching bubbles are wrapped in a large amount of sulfur dioxide. The place where Roland lived before was on the upper side of the platform. He built an isolation layer and heat pipes, and stored a large amount of oxygen for survival, as well as some electronic equipment and detection instruments.

Strictly speaking, if a normal human is here, he can survive with difficulty, but some changes that will adapt to the environment will gradually occur.

"I feel very strange, too." Su Mei said.

"If it is really expanded here, you can even use this hot spring to generate electricity." Lu Yuan said: "In terms of heat exchange, as Roland said before, at least an underground shelter can be built for 2,000 people, and agriculture and breeding can be appropriately developed. The water and thermal conditions here are met, and even photosynthesis must be used."

"But such a good place, after being discovered, was so desolate that only the survivor Roland was trapped here and could not get out."

"What caused the expedition to be wiped out, and what made the refuge so disgusted that when resources were exhausted and self-destructed, they did not have the courage to migrate to the immigrants here."

"It's all too weird and too curious."

The boy said quietly.

Su Mei nodded.

"By the way, where is the bronze door?" Lu Yuan continued.

"Let's detect with metal first." Su Mei said this, then activated the metal detector, and then spoke in surprise: "The bronze door cannot be sensed here."

Su Mei looked at the image generated on his detector: "The place with the most metal objects here is the house where Roland lived before. There are a large number of technological creations, which means a large number of metal components, but other than that, there is no large number of metal reactions here."

"Maybe the bronze door that Roland mentioned is not actually a metallic substance like bronze?" Lu Yuan asked.

"It's probably true, let's search separately." Lu Yuan said: "But if you find a place similar to a bronze door, don't contact it and notify another person immediately."

"Understand." Su Mei said.

At this time, there is really no time to laugh. In such a place, saying that you are not nervous and depressed is really a lie.

After all, this is 500 meters deep underground. Even if this cave has such a setting that must be connected to the outside world, otherwise Sky will feel uncomfortable here, so there is really no need to worry about being buried inside.

But what if this setting fails?

After Lu Yuan discussed with Su Mei, the two separated immediately, and began to search with Roland's door of the room as the center.

The farther away, the more I searched, the more I felt that this place was really a Feng Shui treasure land with sufficient water and heat resources. The only disadvantage was that the sulfur dioxide concentration here was too high and the water quality inorganic salt content was high, so it could not be drunk directly.

However, the high content of inorganic salts means a large amount of mineral resources and fresh water extraction, which is nothing to humans who master the technology of permeable membrane filter elements. There is a lot of space, water heat, and permanent outlets that can directly reach the outside world.

Speaking of this, Lu Yuan suddenly realized a problem, that is, if he said he was building a door at the entrance of the cave, it meant to control the in and out of the personnel.

So will this cave determine that the door is also blocked and then clean it up?

This is a bit ridiculous.

Lu Yuan actually largely observes this cave with a manager's mentality. He also understands that if he has enough resources, it is easy for this cave to accommodate two thousand survivors.

Moreover, geothermal resources are not like coal, oil, and even nuclear energy, and will eventually be exhausted.

Almost as long as the earth still exists, the geothermal heat will not end and will not change because of whether the sun is extinguished or not. People inside can really survive for generations.

Of course the only disadvantage is.

There are no stars here.

At this moment, Lu Yuan suddenly heard Su Mei's voice: "Come and take a look here."
Chapter completed!