I came across an interesting online article with the headline "The Mysteries of the World that has yet to be scientifically solved". Some people might have already known about them, but I would like to summarize and share some of the interesting points here. 1) Baghdad Battery. The clay pot was discovered in 1930s. It had a copper cylinder and it has been proven that the pot was a kind of battery. It is said that it was made in the 2nd century B.C. and the answer to the question, "Why did people need it back then?" remains unclear. 2) Moai statues in Easter Island. There are about 887 statues and each one is an average of 4m high, while some of them weigh 28 tons and are10m high. Human beings have been living on the island since before the 900s. The question "How were they put into place" remains unclear. 3) Gobekli Tepe. This is an ancient ruin located at the top of a mountain. It has over 200 pillars that are 6 meters high and weigh 20 tons, they are arranged in 20 circles. The biggest mystery is "How were they built" and "What is their purpose?" I haven't known about these items or been to those spots before. I guess I want to visit them and go see for myself in the future.