1) The Age of Exploration, during the 15th and 16th centuries, saw European explorers such as Christopher Columbus and Vasco da Gama reach new lands and establish trade routes.

2) Cristiano Ronaldo is a Portuguese professional soccer player widely regarded as one of the greatest footballers of all time. He has won numerous awards, including multiple FIFA Ballon d'Or titles, and has played for top clubs such as Manchester United, Real Madrid, and Juventus.

3) The ancient city of Pompeii was preserved under layers of volcanic ash after the eruption of Mount Vesuvius in 79 AD, providing valuable insights into Roman life.

4) The Arctic Ocean is the smallest and shallowest ocean, located at the North Pole. It is covered by sea ice for much of the year.