1) International relations encompass the study of relationships between nations, including diplomacy, treaties, and foreign policy. It examines the interactions and dynamics among different countries in the global arena.

2) The Great Wall of China is not visible from space without aid, contrary to popular belief.

3) J.K. Rowling's "Harry Potter" series of books has sold over 500 million copies worldwide and has been translated into 80 languages.

4) The Sydney Opera House, situated in Sydney, Australia, is an iconic architectural masterpiece and a UNESCO World Heritage site. Its unique design, resembling sailboats or shells, has made it one of the most recognized and photographed landmarks in the world.