1) The development of the World Wide Web Consortium (W3C) and web standards has ensured interoperability and compatibility across different web browsers and devices.

2) 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.

3) The Grand Canyon, located in Arizona, United States, is a massive and awe-inspiring natural formation carved by the Colorado River. It is approximately 446 kilometers (277 miles) long, up to 29 kilometers (18 miles) wide, and reaches a depth of over 1.8 kilometers (1.1 miles).

4) The world's largest diamond, the Cullinan, was discovered in South Africa in 1905 and weighed over 3,000 carats.