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1. Is the most populous one.
As of 2019, UK has passed France according to this source.
United Kingdom
France
Spain
Italy
2. Was once in the hands of the Muslims.
The whole Iberian peninsula was in the Umayyad hand except the northern parts. It wasn't until 1492 the Emirate of Granada fell into Catholic monarchs.
France
Italy
Spain
United Kingdom
3. Is the most visited country in the world.
86.9 mil. people visited France in 2017.
United Kingdom
France
Italy
Spain
4. Had the least amount of colonies.
United Kingdom
France
Italy
Spain
5. Has the largest economy of them all (in the nominal method).
France is only a hundred thousand US dollars behind UK.
France
United Kingdom
Italy
Spain
6. Most of world's UNESCO World Heritage Sites are in here.
54 sites for Italy, Spain is in the 2nd place with 47 sites.
France
United Kingdom
Spain
Italy
7. Is the largest producer of wine.
Italy leads the rank with France and Spain coming in 2nd and 3rd.
United Kingdom
Spain
France
Italy
8. Its national animal is bull.
Italy
France
United Kingdom
Spain
9. Was the first to abolish slavery.
UK did not abolished the practice of slavery
France
Spain
Italy
United Kingdom
10. Has two other countries inside itself.
San Marino and Vatican City are inside Italy
United Kingdom
France
Italy
Spain
11. Its capital city's Roman name was "Lutetia".
United Kingdom
Italy
France
Spain
12. The oldest building still under construction is located in here.
Located in Barcelona, Sagrada Família's construction started in 1882 and is still unfinished.
France
Spain
United Kingdom
Italy
13. Its highest point is the lowest one among the others.
United Kingdom
Spain
France
Italy
14. First country to introduce the license plate.
United Kingdom
Spain
Italy
France
15. Was neutral during the WWII.
France
Spain
Italy
United Kingdom
16. Has the shortest coastline of them all.
Spain
Italy
United Kingdom
France
17. Its alliance with Portugal is the world's oldest.
Italy
France
United Kingdom
Spain
18. Has the highest life expectancy.
Spain
United Kingdom
Italy
France
19. The only country to NOT name itself on its stamps.
France
Spain
Italy
United Kingdom
20. The largest anti-war rally took place.
In 2003 the protest involved around 3 million people that protested against the Invasion of Iraq.
Start by naming any country that France borders. Then name any country that borders any of those countries. Then keep going until there are no more countries left to name.