This is how Antoine de la Sale, in his *The Paradise of Queen Sibyl*, describes the cave entrance as it appeared to him on May 13, 1420, during his ascent of Mount Sibilla:
"...Thus, following the winding path, one climbs the mountain to the summit, facing the rock known as the mountain's crown, where the cave entrance lies... To the right is the entrance—small and shield-shaped, tapering at the top and widening at the bottom. A rock stands before it, requiring those who wish to enter to stoop low and crawl inside, sliding their feet downward until they reach a small, square chamber to the right of the opening, featuring stone seats carved all around the walls. It measures between eight and ten paces in length, width, and height; there is also a circular hole, the size of a man's head, through which only a pale light filters due to the mountain's immense thickness. Leaving this room, anyone wishing to proceed further must turn right; however, one must advance feet-first, as the cave is so narrow, cramped, and steep that no other way is possible..."
The writer's personal experience ends here, though he goes on to recount the story of some young men from Montemonaco who ventured into the passage to the right of the first chamber; they reportedly reached a corridor swept by a fierce wind and, terrified, turned back. Two German gentlemen, accompanied by the priest Antonio Fumato, reportedly—according to La Sale’s account—made their way past the "wind tunnel," crossed the bridge over the abyss, and got past the two dragons with flaming eyes, finally reaching the "...metal gates that clang day and night..."—the true entrance to Queen Sibyl’s subterranean realm.
La Sale records that, at the time of his ascent (1420), the entrance was clear, allowing access to at least the first chamber.