During this day's search, the two did not find any useful clues, in the vast underground city, every place, there were traces of human activities, but they couldn't see a single person, even a corpse, they didn't see it.

In the hub of the city, in the city's main control room, there were no staff members in sight either.

All the instruments and equipment in the underground city, as well as the infrastructure, are running automatically, and even the underground vehicles are also running in an orderly manner according to the established pattern.

The entire underground city is filled with an extremely eerie atmosphere.

What is it that can make such a huge underground city empty?

Zhao Yuan could not give a reasonable answer.

Xue Yi, as an awakened human being, cannot be explained by science.

Of course, the two of them did not gain nothing, in addition to scraping a lot of useful things, Zhao Yuan also harvested a pair of exoskeleton mechas, and in addition, they also figured out the war that only heard their voices and did not see them.

The credit goes to Xue Yi, and when the two arrived at the city's main control room, Xue Yi quickly understood the ins and outs of the matter.

Everything originates from the huge metal crust of the underground city, in fact, it is a huge instrument, and when it is hit by an external force, it will produce a force and form a qi, and at the same time, it will simulate the sound of ancient wars......

……

Many things, as complex as they may seem, are simple.

And a dungeon without one person is incomparably complicated.

Zhao Yuan is a cultivator with vast magical powers, and Xue Yi is an awakened human with profound knowledge, but with the strength of the two of them, they can't explain why the dungeon is without a single person, as if in an instant, all the people have disappeared.

Zhao Yuan believed that even the most powerful gods of the cultivators could not do this.

It's easy to destroy a dungeon, but it's simply impossible to make hundreds of millions of humans disappear in the dungeon at the same time without destroying the dungeon.

Regarding the number of human beings, Zhao Yuan and Xue Yi reached a consensus, and they both believed that the number of human beings living in this dungeon exceeded at least 100 million, and this was still an extremely conservative estimate.

For the next three days, Zhao Yuan searched for the next three days, and he believed that he would always be able to find a little clue.

And Xue Yi, in the past three days, is also looking for clues in the city's main control room.

Zhao Yuan found nothing, but Xue Yi gained a lot, because she deciphered the city code, entered the city's main control optical brain, and called up the monitoring system of the entire city.

Under the surveillance information, the prosperous side of the city was presented in front of the two.

Busy traffic, bustling, some warm families, some tearful stories.

The surveillance screen made Zhao Yuan feel as if he had returned to the earth.

This is a city that is very similar to the earth, the only difference is that it is underground, of course, the level of science and technology here is much higher than that of the earth, and the human quality here is not comparable to the earthlings, as for the spirit and material, between the two, it is not at the same level.

Such a powerful civilization suddenly disappeared, leaving behind only a ruins beyond human imagination.

No result.

Even if a large number of surveillance videos were found, there was still no result, because the surveillance video did not record the process of the sudden disappearance of human beings......

……

Starlight is like silver.

Zhao Yuan and Xue Yi sat side by side by the lake, looking at the vast stars in the sky.

"When are we leaving?" Xue Yizhen leaned on Zhao Yuan's shoulder very naturally.

"Let's go?" Zhao Yuan smelled the faint fragrance emanating from Xue Yi's body, and a wry smile appeared on his face.

"What's wrong?" Xue Yi sat upright, and she sensed a hint of something bad from Zhao Yuan's tone.

"I don't have coordinates, and here, there is no teleportation array. Zhao Yuan sighed.

"You mean that you can't get out of here at all?" Xue Yi looked at Zhao Yuan in surprise, she remembered that Zhao Yuan said with confidence that he could leave here.

"I might be able to leave. Zhao Yuan hesitated.

"Because of me?" Xue Yi Bingxue asked immediately.

"This ...... There is a little ......" Zhao Yuan wanted to speak and stopped.

"Say, I don't mind. Xue Yi sat upright, her face calm.

"Although I didn't return to the coordinates of the Battle Cloud Continent, and I didn't have a teleportation array, however, I can use the stupidest way to fly out of here, I just need to choose a direction and keep flying, it doesn't matter if the direction is right or not......"

"What you mean is that you can fly all the time, for decades, hundreds of years, or even thousands of years, because you are a half-immortal body, and you don't care about time at all, in this boring flight, you can cultivate, you can run your own Lingtai World, in fact, you will not be lonely, because, you have the Lingtai World, and in your Lingtai World, you have countless people, who can not only provide you with food, but also provide you with a steady stream of faith power...... One day, you will encounter a planet inhabited by humans while flying, and if you are lucky, you will encounter an ancient teleportation array, and you can directly reach the human world......"

"Yes. Zhao Yuan looked at Xue Yi blankly, he didn't expect Xue Yi to guess his mind at once.

"I've become a burden again. Xue Yi showed a bitter smile on her face.

"No, I'm not going to leave for a while. Zhao Yuan shook his head.

"For what?" Xue Yi's eyes lit up.

"If you don't have a goal in flying in the vastness of the universe, time has lost its meaning, so what's the point of decades earlier and decades later? ”

"Stay with me, until I'm old?"

"Ahem......"

"And then, you're going to get out of here?"

“……”

"If so, I'd rather go with you. Xue Yi said lightly.

"I think flying in the stars is very boring......"

"I'd rather endure the endless boredom than delay even a day, because you still have four women waiting for you, and the kind of interstellar flight you talked about, encountering human settlements and teleportation arrays, is completely a matter of chance, perhaps, on the third day we leave here, if we are lucky, we will be able to encounter an ancient teleportation array left by the gods. ”

“…… This ......"

Zhao Yuan opened his mouth, and he wanted to speak, he was entangled in this question, because, when he was flying in the interstellar space, he happened to encounter a meteorite belt, and he met a monkey against the sky, which is enough to show that there is a big difference between leaving early and leaving late.

"You have two choices, first, abandon me here, and second, take me away!"

"You...... Not afraid of loneliness?"

"Don't be afraid. Xue Yi's clear eyes showed an extremely resolute look.

"Alright, once your lessons are out, let's go. ”

"Good. ”

……

The so-called curriculum is to use the equipment in the dungeon to develop the curriculum, and the content of the curriculum is mainly to teach some basic scientific knowledge, including the curriculum from basic education for young children to higher education.

Because Zhao Yuan and Xue Yi are leaving, the only way is to arrange the class on the computer.

The people in the meteorite belt belong to the people of the cold weapon era, and it is undoubtedly a fool's dream to let them fully master the technology of the dungeon, so Xue Yi's course is mainly to master some simple operations, more courses, and focus on the education of new children.

If you follow the curriculum education arranged by Xue Yi, at most forty years, you can cultivate a group of young people who can use the equipment of the dungeon, of course, if you want to fully digest the scientific knowledge of the dungeon, it will take at least a hundred years, and they will need to continue to explore.

No one can predict what kind of civilization the hunters will be able to breed on the basis of the dungeon, after all, there are too many human factors, and the slightest disconnection may lead to another direction of development.

What Xue Yi did was just to do her best, if nothing else, according to Xue Yi's arrangement, this planet would be brilliant again.

The dungeon provides an almost perfect living space for the hunters who migrate here, here, there is no need to worry about life at all, and there are no natural enemies, even if there are invaders from the outside, the defense of the dungeon is enough to resist most of the strong people.

So far, Zhao Yuan still hasn't figured out the principle of the generation of those gangqi, after all, it doesn't belong to the category of science, of course, it doesn't belong to the category of cultivation, if you insist on finding a reasonable explanation, it can only be said that science combined with cultivation to create a miracle.

Xue Yi worked at full capacity for five days and finally finished her work.

I have to say that Xue Yi is a careful woman, and her courses, in addition to telling adults to master some simple mechanical operations, have been arranged for young children until they are thirty years old.

If Xueyi completes all of the courses, then the adult child will become an excellent scientist.

After the course, Xue Yi still has a lot of arrangements, that is, when all the courses are completed, some more esoteric knowledge will appear gradually, when the learner himself knows how to control the equipment of the dungeon and begins to study purposefully, Xue Yi's work is truly completed......

……