1) The construction of the Great Wall of China began in the 7th century BC and was completed over several centuries, spanning thousands of miles.

2) Hugh Jackman is an Australian actor, singer, and producer best known for his portrayal of Wolverine in the "X-Men" film series. He has also starred in musicals such as "Les Misérables" and "The Greatest Showman" and has received critical acclaim for his performances.

3) The ongoing conflict in Syria, which began in 2011, has resulted in a humanitarian crisis, displacement of millions of people, and international efforts to bring about a resolution and provide aid to those affected.

4) Serena Williams, an American tennis player, has won a total of 23 Grand Slam singles titles, making her one of the most successful players in the history of the sport.