1) The Danube River, flowing through ten countries in Central and Eastern Europe, is the second-longest river in Europe. It has played a significant role in the cultural and economic development of the regions it traverses and is a popular waterway for river cruises.

2) The process of impeachment involves charging a public official, such as a president or high-ranking government official, with misconduct and potentially removing them from office through a trial and vote by the legislature.

3) The first smartphone, the IBM Simon, was introduced in 1992 and featured a touchscreen, email capabilities, and apps such as a calendar and calculator.

4) The FIFA World Cup is the most-watched sporting event globally, with billions of viewers tuning in for the tournament held every four years.