Zuko held a flame aloft as he surveyed his surroundings, unable to help marveling inwardly. He had never expected a secret passage like this to exist.
They were currently walking through a secret passage leading to the Royal Palace, one of the countless secret passages within it.
Back when Kori had helped them search for the secret room containing Yin Shu's letters, she had also discovered quite a few secret passages along the way.
Their main task at the time, however, had been finding the secret room, so they had not explored those passages in depth, though they had quietly committed the information to memory.
After finding the secret room, they had begun exploring those passages, primarily to determine their entrances and exits, how to enter and leave them, and the various mechanisms inside.
They had called this the [Royal Palace Deciphering Operation].
Both he and Kahn had participated, but exploring and deciphering the secret passages had been difficult and dangerous. By the time he was banished, they had only gained a sufficient understanding of two or three passages, and this one was not among them.
Clearly, the operation had not stopped after his departure. This passage must have been newly discovered during his time away.
The purpose of a passage leading from the Royal Palace to outside the Imperial Capital's walls spoke for itself: naturally, it was meant to allow members of the royal family to flee in times of grave danger.
This was a one-way passage. The switches for the mechanisms blocking the route were hidden on the inside, ensuring that people could only leave the Royal Palace for the outside of the city, rather than enter the Royal Palace from outside.
At the same time, these mechanisms ensured that even an Earthbender intruder would be delayed considerably