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

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

3) The world's first stock exchange was established in Amsterdam in 1602.

4) The fall of the Berlin Wall in 1989 symbolized the end of the Cold War and the reunification of East and West Germany.