The Pentagon Papers revealed previously undisclosed details about U.S. involvement in Vietnam.

The ocean contains structures larger than mountain ranges.

Some butterflies migrate across continents.

The largest living structure on Earth is the Great Barrier Reef.

The Roman navy played a key role in Mediterranean dominance.

The Aztec capital Tenochtitlan had a population of around 200,000 in the early 16th century, larger than most European cities.

The highest navigable lake in the world is Lake Titicaca, shared between Peru and Bolivia at 12,507 feet.

The Age of Exploration connected continents through sea travel.

In 1932, Australia deployed machine guns against flocks of emus during the Emu War.