Beyond the answers - interesting background to this quiz

A railway that spans two continents

The Trans-Siberian Railway is the longest railway line in the world, stretching roughly 9,000 kilometres from Moscow to Vladivostok on the Pacific coast. Construction began in 1891 and the route was completed in stages over the following years, opening up vast regions of Siberia. Even today, the full journey takes about a week by train, crossing seven time zones along the way.

The last surviving element of its kind

Niobium, with the symbol Nb, was named after Niobe from Greek mythology, a figure associated with tears and mourning. For a long time it was confused with tantalum, a chemically similar element named after Niobe's father, Tantalus. Niobium is used in superconducting magnets and in steel alloys, and it is one of the elements that occurs naturally on Earth in only tiny quantities.

A city built on water

Venice is famous for its canals, but it is not the only city with that nickname - Amsterdam, Bruges and Saint Petersburg all have claims to waterborne fame. What sets Venice apart is that the entire historic centre sits on a lagoon, built across more than a hundred small islands linked by bridges. The city has been slowly sinking for centuries, and flooding has become a recurring concern.

The apple, the moon and a law of nature

Isaac Newton published his law of universal gravitation in 1687 in the Principia, one of the most influential scientific works ever written. The familiar story of an apple falling on his head is probably embellished, but Newton himself did mention an apple in later recollections. His insight was not just that things fall, but that the same force keeps the Moon in orbit around the Earth.

A small country with a big mountain range

Andorra sits high in the Pyrenees between France and Spain, and it is one of Europe's smallest states, with a population of well under 100,000. It is also one of the few countries in the world with two heads of state - the President of France and a Spanish bishop, a legacy of a medieval arrangement. Its economy leans heavily on tourism and duty-free shopping.