C3446 A Few Meters Less

There's no Hidden Door that leads to the basement? Could it be that my guess is wrong! Or perhaps... there is a place that I missed out on?

Lu Shan searched the first floor a few times but still found nothing. He could not help but be deeply suspicious of himself.

He ran through it from the beginning to the end, and then he felt that his deduction should be correct. Logically speaking