Why? The Pacific covers about 165 million square kilometres — roughly a third of Earth's surface.

Why? The Indus rises near Lake Mansarovar in the Tibetan plateau.

Why? The Nile is traditionally considered the longest at about 6,650 km, though the Amazon dispute exists.

Why? Bern is the political capital; Zurich and Geneva are the larger economic hubs.

Why? Ankara replaced Istanbul as capital in 1923 under Mustafa Kemal Atatürk.

Why? Ottawa was chosen by Queen Victoria in 1857 as the capital of Canada.

Why? Canberra became the federal capital in 1913 as a compromise between Sydney and Melbourne.