1) The word "mountain" contains three vowels: O, U, and A.

2) The world's tallest waterfall is Angel Falls in Venezuela, with a height of about 3,212 feet (979 meters).

3) 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.

4) The word "flower" contains two vowels: O and E.