1. The Great Wall of China was primarily built to protect against invasions from which group?

2. To what does the name 'Big Ben' technically refer?

3. What is the geological term for an isolated mountain like Uluru that rises abruptly from a plain?

4. What is the most common geometric shape of the basalt columns at the Giant's Causeway?

5. What surprising factor has helped the Leaning Tower of Pisa survive multiple earthquakes?

6. What did the Old Russian word for 'Red' (krasnaya) also mean when the square was named?

7. What did architect Bernini intend the massive colonnades of St. Peter's Square to represent?

8. Under which Ottoman Sultan did construction of the Grand Bazaar begin?

9. What caused the 'starlight' holes in the iron roof of Souq Al-Hamidiyah?

10. What was the name of the underground complex of tunnels and elevators beneath the Colosseum's arena floor?

11. What makes the Tower of Hercules unique among all other Roman lighthouses?

12. According to local legend, how did Guru Padmasambhava reach the site of the Tiger's Nest?

13. The tripod-shaped structural system used to stabilize the Burj Khalifa is known as what?

14. The water for the Trevi Fountain is supplied by which ancient Roman aqueduct?

15. What environmental benefit does the Rain Vortex provide to the Jewel Changi complex?

16. In what year did the Maracanã host its first FIFA World Cup final with a record-breaking crowd?

17. What natural disaster in 1117 AD destroyed the outer ring of the Arena di Verona?

18. The superconducting magnets in the LHC are cooled to a temperature colder than what?

19. What is Bangkok known as in Thai?

20. Which famous river runs through Bangkok?