Introduction to Stone City: Machu Picchu is a stone city. All buildings are made of huge stones. Each stone is polished very smooth. There is no adhesive between the stones, but they fit together perfectly. Even Even the thin blade cannot be inserted, which is amazing. It is said that one of the stones has 33 corners, and each corner is closely integrated with the corners on the adjacent stone. With such sophisticated construction, meticulous planning, and astonishing weight, I really don’t know how people at that time transported the huge stone up the mountain and detailed it carefully. Parted and polished.