C212 Catacombs

The walls were old and yellow. Yellow class can not be repudiated. One could tell with a glance that it had been many years. Strangely, the four walls were made of iron, and if one were to touch them lightly, they would emit a sound.

That reminds me of something in a book.

Legend has it that there is a clear and detailed explanation for it in the book, "Qin Dynasty Eunuch has a tomb