Does the "underground palace" in the movie "The Myth" really exist? What is an ‘underground palace’?

The underground palace definitely exists, and generally refers to the emperor's tomb. If you visit the Ming Tombs or Xiaoling Tombs once, you will hear this word from the tour guide again and again.

As for whether that kind of environment will exist, it’s hard to say. Just because something we don’t know doesn’t mean it doesn’t exist. The Mausoleum of Qin Shihuang has never been opened so far. No one knows what it is like inside. Don’t underestimate the wisdom and power of the ancients.