Just as the Qi Sanbiaozi was troubled, Pang Dun was the first to rush forward, wanting to test just how heavy this Stone Door was.

Pang Dun's reminder had a lot of strength behind it, but no matter how hard he tried, the two obsidian stones in front of him didn't budge an inch.

Looking at Pang Dun's panting, Fang Zishu said softly, "Come back Pang Dun, these two pieces of Obsidian Stone are extremely heavy, each of them have a weight of at least a thousand jin, and you are just one person. No matter how strong you are, you will not be able to open them."

"If this door weighs over a thousand catties, then we would not be able to open this Stone Door at all!" Pang Dun's face was filled with regret.

Ever since they had entered this natural tomb, they had experienced far too many things, many of them even coming across fatal dangers. They had finally made it to the present, and reached the true tomb of the Monarch of the Northern Wei Dynasty, which was the Stone City in front of them.

But now, they were stopped by the two sets of Obsidian Stone Door at the city gate. This was something that Pang Dun could not accept.

Fang Zishu laughed indifferently, "That's right, with the strength that we have, even if we gather all of them together, we will still not be able to open this Stone Door. However, I think that although this Stone Door is incomparably heavy, it is definitely not something it cannot open, it is only that we have yet to find a way to open it."

"I agree with Brother Fang!"

Qi Sanbiaozi nodded, pointed to the two gigantic diagrams on the black key door and said: "Could the mechanism to open the Stone Door be hidden within the diagrams?" The pattern Qi Sanbiaozi mentioned was the engraved 'door bolt' on the two obsidian gates.

In that era when technology wasn't developed, they didn't want to have automatic locking doors or induction doors at all times. In ancient times, doors were mostly made up of 'handles', 'bolts' and 'crossbars'.

The two circles on the Stone Door were about the size of bowls. Not only were they used as knocks, they also served as handles.

"Perhaps there is some kind of mechanism that can open the Stone Door inside the 'door lock'. We should carefully search for it."

After the Professor Xu finished speaking, he walked up to the door and used his dry and dry hands to constantly rub the black Stone Door s. He wanted to find the mechanism to activate the Stone Door from the sculptures engraved on the door.

But after a long while, the Professor Xu touched the carving again and again, but he could not find any useful clues, much less news about mechanisms that could open Stone Door s. Although everyone knew that the Monarch of the Northern Wei Dynasty's Main Tomb was definitely hidden in the Stone City, but now that the Stone Door could not be activated, no matter how many ideas they had, it would be difficult.

Moreover, they were not at the cliffs on either side of the moat, but outside the city walls.

The thing that caused them to despair the most was that the height of the black city wall before their eyes had far surpassed the moat they had crossed previously. Facing the wall which was over ten meters tall and without any force that could be used to climb, no matter how skilled Da Zeng was in climbing, it was impossible for him.

Just as everyone started to despair, Fang Zishu continued to walk back and forth along the black city walls.

"Brother Fang, what are you doing?" Qi Sanbiaozi could not help but ask.

But Fang Zishu did not answer his question. Instead, he moved even faster.

Under the crowd's gaze, Fang Zishu practically walked through the several tens of meters of the city wall outside the Stone Door, and it was not only this, because Fang Zishu once again turned around and stood at the side of the cliff. Not far from his feet was the six to seven meter deep dried up moat.

But Fang Zishu did not care about that, he kept looking to the side, as if he was calculating something.

After a long while, Fang Zishu finally nodded his head, and took out the 'compass' from his bag.

Previously, when Fang Zishu wanted to test whether those 'Red spot and green feather bat' who committed suicide by hitting the cliff had been disturbed by the magnetic field, he had taken out the compass to have them tested. It was at that time that Fang Zishu was certain that they had already left the area affected by the magnetic field.

Sure enough.

Fang Zishu saw that the needle on the compass in his hand did not deviate at all.

This meant that the magnetic field was natural and no man-made changes had occurred. Through the information he obtained from walking back and forth, coupled with the compass's second measurement, Fang Zishu finally confirmed one thing, something that had troubled him for a long time.

"There's a problem with the direction of this Stone City."

Seeing Fang Zishu being so busy, Professor Xu and the rest thought that he had already thought of a way to open the Heavy Stone Door. But they didn't expect that the first thing Fang Zishu said was actually related to the location of the Stone City.

"Master Fang, now is not the time to survey Feng Shui and Geography. We only need to finish one thing, and that is to activate this Stone Door. Otherwise, everything that follows will just be empty talk." Professor Xu couldn't help but remind him.

"I know." Fang Zishu nodded his head: "What I am talking about right now is whether or not we can open these two Stone Door s."

"Activating the location of the Stone Door and this Stone City? Is there a need to link the two? "

The Qi Sanbiaozi did not understand what Fang Zishu meant, but after getting along with him for such a long time, he knew that Fang Zishu was not someone who would speak nonsense, so since he said it like that, he must have his own reasons.

Seeing that everyone was looking at him, Fang Zishu did not keep them in suspense and immediately explained to them.

According to the《 Heavenly Star Fengshui》, tombs would usually be constructed in places with 'Qi' or 'dragon veins'. For example, the tomb of 'Zhufu Yan' that Fang Zishu had previously discovered was the most typical tomb.

To compare the most pure and vast source of water in the middle level of Ao River with a 'water dragon', combined with two bulging hills, and looked towards' Lancang 'and' Wu Tu 'from the east. It was the typical pattern of mountains and rivers intertwining together, this pattern was known as' Azure Dragon Water Gathering 'in the《 Heavenly Star Hydro》.

Zhufu Yan was not an ordinary person either. He had constructed his own mausoleum under the ground, and the entrance could only be opened with moonlight shining on it and the stars hanging in the sky. In front of him was the 'Azure Dragon Gathering Water', and then there was the 'Celestial Body Moon God'.

With the 'Triple Refinement and Three Space Formations' as the foundation, this was the reason for creating such an awe-inspiring, enormous underground palace!