Special Attraction

Caves and Natural Architecture Yesterday I experienced a peculiar event. I took a wrong turn and entered a rather dreary-looking forest where some strange skeletons tried to attack me. I barely managed to find refuge inside a cave, but when I was in the cave, I was overcome by a question. How can this cave, especially its entrance, be so round yet manage to hold itself up and not collapse? Even if I wanted to make an artificial cave in sturdy rock, wouldn't the pressure and resistance make it collapse? We just lack the knowledge and technology to make caves like nature can. Maybe in the distant future, we will be able. Truth unveils its logic in order. ※ This adventure log must be completed in order.