1) The Great Wall of China is a UNESCO World Heritage site and one of the most iconic man-made structures in the world. It stretches over 21,196 kilometers (13,171 miles) and was constructed to protect the Chinese empire from invasions during ancient times.

2) Male seahorses are the ones who give birth to their offspring.

3) The world's first stock exchange was established in Amsterdam in 1602.

4) The Olympic Games, originating in ancient Greece, were revived in 1896 and are now held every four years, bringing together athletes from around the world.