The entire structure was actually very simple. If the Stargate were compared to an iron ring, then you could roll a sheet of paper into a tube and pass it through the ring. That was the overall design: the paper tube was the tunnel, and the iron ring was the Stargate.
Vehicles passed through the inside of the tunnel. As for what lay outside the tunnel, they had no idea.
However, this had one drawback: it was not very convenient to observe or study the Stargate.
They could only reserve enough space in the airspace outside the tunnel to study the Stargate from the outside.
The reason for choosing this design was that some people had no right to know of the other world's existence, yet their manpower had to be used when hands were short. This structure provided enough ways to keep the truth hidden from them.
That was one reason. The second was mainly aimed at the people of Great Qin and the Song Dynasty. At present, no one in Great Qin besides Dai Yuan knew of the Stargate's existence, and Dai Yuan would not speak of it. They had already deployed enough personnel within Great Qin, and quite a few factories had been built there.
There were also enough schools, all of which needed people to keep running. In contrast, if trade, mines, and other resource exchanges were established with the Song Dynasty, the main workforce for occupying the territory could only rely on the people of Great Qin.
They could not let the people of Great Qin learn of all this, so disguising the Stargate this way was the best solution.
As it happened, because of the Symbiotic Stargates, the passage of time on both the Great Qin and Song Dynasty sides was almost exactly the