1) The word "computer" contains three vowels: O, U, and E.

2) The oldest known musical instrument is a flute made from a bird bone, estimated to be around 43,000 years old.

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

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.