1) The Great Barrier Reef in Australia is the largest coral reef system in the world and is visible from space.

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

3) The strongest natural material known to man is spider silk. It is stronger than steel and more flexible than nylon.

4) The largest living structure on Earth is the Great Barrier Reef, spanning over 2,300 kilometers (1,400 miles) along the coast of Australia.