1) The word "guitar" contains three vowels: U, A, and I.

2) 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.

3) Cyclones, also known as hurricanes or typhoons, are powerful tropical storms characterized by low-pressure centers and strong winds.

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.