1) The tongue of a blue whale is so big that about 50 people could stand on it.

2) The discovery of the Americas by Christopher Columbus in 1492 opened up new trade routes and had a profound impact on world history.

3) 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.

4) The concept of self-driving cars, or autonomous vehicles, is being actively developed by companies such as Tesla, Google (Waymo), and Uber.