1) The impact of social media platforms on society and politics has been a subject of debate, including concerns about misinformation, privacy, online harassment, and the influence of these platforms on public opinion and democratic processes.

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

3) The Russian Revolution in 1917 resulted in the overthrow of the monarchy and the establishment of a communist government under Vladimir Lenin.

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.