Inside Emperor Wanli's underground tomb. [Photo provided to China Daily]

The circular part, known as bao cheng, or the treasure city, has at its heart a big earth dune that rises to more than 10 meters above the ground. Since the burial chamber was most likely to be deep in the ground and directly under the peak of this symbolic burial mound, the question had always been: How to approach it?

The broken wall might be the place. And remember, this was in May 1956.

"The bricks had gone and there was a big hole about half a meter in diameter," Yang says. "Since it was three meters above the ground, the team members had to set up a human ladder to reach the hole and take a peek inside. It was a peek that would change the contemporary history of the Dingling Mausoleum."

The rim of the hole appears to its examiners like the upper edge of an arched gate. Peeking inside, the man at the top of the human ladder also glimpsed brick marks－marks left on earth indicating the previous existence of bricks. What according to some villagers had been a hiding place for local bandits reminded the archaeologists of the entrance to a secret tunnel.