Beyond the answers - interesting background to this quiz

The holy city that draws millions every year

Mecca, in Saudi Arabia, is the birthplace of the Prophet Muhammad and the holiest city in Islam. Every year millions of Muslims travel there for the Hajj pilgrimage, which all able-bodied believers are expected to complete at least once in their lifetime. Non-Muslims are not permitted to enter the city itself, making it one of the most restricted destinations on Earth.

The world's youngest capital city

Ngerulmud, the capital of Palau, is often described as the smallest capital city in the world by population. It was built in the early 2000s on the island of Babeldaob, replacing the previous capital, Koror. The complex was designed with a distinctive capitol building inspired by the United States Capitol, reflecting Palau's close historical ties with the United States.

Two very different mountain chains

The Rockies and the Appalachians are the two largest mountain ranges in the United States, but they could hardly be more different. The Appalachians are among the oldest mountain ranges on Earth, worn down over hundreds of millions of years. The Rockies are much younger and still growing, which is why they remain dramatically taller and sharper.

A river that crosses ten countries

The Danube flows through ten countries - more than any other river in the world - passing through Germany, Austria, Hungary, Serbia and Romania, among others, before emptying into the Black Sea. Its total length of roughly 2,850 kilometres makes it the second-longest river in Europe after the Volga. It has served as a trade route and a natural border for centuries.

The wonder that may never have existed

The Hanging Gardens of Babylon are the most mysterious of the Seven Wonders of the ancient world. Unlike the pyramids or the lighthouse of Alexandria, no archaeological trace of them has ever been found, and some historians argue they may have been a legendary rather than a real structure. Ancient writers described terraced gardens with exotic plants, supposedly built for a homesick queen.