1) In Norse mythology, the World Tree, known as Yggdrasil, is a massive ash tree that connects the nine realms of existence. It is considered the center of the cosmos and serves as a conduit between different realms, including Asgard (realm of the gods), Midgard (realm of humans), and Helheim (realm of the dead).

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

3) Usain Bolt of Jamaica holds the world records for the 100 meters and 200 meters sprints, with times of 9.58 seconds and 19.19 seconds, respectively.

4) The first modern health insurance policy was introduced in Germany in the late 19th century.