If you add up all the lakes of Africa, South America, Asia, Europe, and Australia, you still get fewer than in one country. Canada has more lakes than the rest of the world combined — roughly six out of every ten large lakes on the planet, almost nine hundred thousand of them. The usual explanation is that Canada is huge, cold, and northern. But that doesn't work: Russia is bigger, Siberia is just as cold, and Brazil gets far more rain. So the real answer isn't in Canada's climate today. It's in what happened to this land thousands of years ago.

In this video we break down why Canada has so many lakes, starting with the Canadian Shield — ancient hard rock, nearly four billion years old, that holds water at the surface instead of letting it drain away. Then we follow the Laurentide Ice Sheet, up to three kilometers thick, and the three things it did as it crept across the continent: it stripped the soil, gouged out hundreds of thousands of hollows, and dumped ridges of rock that dammed the water into new lakes.

We look at the vanished Lake Agassiz, why the land around Hudson Bay is still rising a centimeter a year, and why Siberia — just as cold — never grew the same ice sheet, because a giant glacier needs snow, not just frost. And we end on the hidden cost: the glacier scraped Canada's fertile soil south into the American Midwest, leaving Canada the water and giving Iowa, Illinois, and Ohio the farmland.

The world has a structure. Let's keep finding it.