1) The world's largest ocean, the Pacific Ocean, covers an area of approximately 63 million square miles.

2) The Amazon rainforest produces more than 20% of the world's oxygen.

3) The Federal Reserve System, often referred to as the Fed, is the central banking system of the United States.

4) 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.