1) The word "yesterday" contains three vowels: E, A, and A.

2) 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.

3) In Norse mythology, Valhalla is a majestic hall located in Asgard, the realm of the gods. It is the afterlife destination for brave warriors who die in battle, where they are greeted by the Valkyries and engage in feasting, drinking, and preparing for the final battle of Ragnarok.

4) The world's oldest tree is believed to be a bristlecone pine named "Methuselah" in California, estimated to be over 4,800 years old.