1) The first modern Olympic marathon race was held at the 1896 Olympics in Athens and has since become one of the most iconic and challenging events in athletics.

2) The ozone layer, located in the Earth's stratosphere, protects us from harmful ultraviolet (UV) radiation.

3) The Great Wall of China is not visible from space without aid, contrary to popular belief.

4) The word "telephone" contains five vowels: E, E, O, E, and E.