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

2) The fingerprints of koalas are so similar to humans that they have been mistaken at crime scenes.

3) The world's first credit card was introduced in 1950 by Diners Club.

4) The concept of federalism involves the division of powers between a central government and regional or local governments, allowing for shared governance and autonomy for different levels of administration.