1) The Eiffel Tower can be 15 cm taller during the summer due to thermal expansion.

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

3) The largest insurance market in the world is Lloyd's of London, which is not an insurance company but a market where insurance brokers and underwriters come together.

4) The phenomenon known as "black holes" occurs when matter is crushed into an infinitely small space, creating a gravitational pull so strong that nothing can escape.