1) Mount Kilimanjaro in Tanzania is the highest mountain in Africa and attracts climbers from around the world.

2) The Amazon rainforest produces more than 20% of the world's oxygen.

3) The first modern Olympic marathon race was held at the 1896 Olympics in Athens and has since become one of the most iconic and challenging events in athletics.

4) The concept of proportional representation, used in some electoral systems, aims to ensure that political parties' representation in government aligns more closely with the proportion of votes they receive from the electorate.