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 total length of your blood vessels can circle the Earth more than twice.

3) The term "bull market" refers to a period of rising stock prices, while a "bear market" refers to a period of falling stock prices.

4) The construction of the Great Wall of China began in the 7th century BC and was completed over several centuries, spanning thousands of miles.