The Orinoco starts in the highlands near the border with Brazil, then makes a giant curve across Venezuela before reaching the Atlantic Ocean. Along the way it picks up water from hundreds of smaller rivers, growing wider and wider as it goes.
The river is famous for something strange: where it passes near the Amazon, a smaller river called the Casiquiare connects them. It is the only natural channel in the world that joins two huge river systems together. Boats can travel between the Orinoco and the Amazon without ever leaving the water.
All sorts of animals live in or near the Orinoco. Pink river dolphins swim through the milky brown water. Capybaras (the world's largest rodents, about the size of a sheep) graze on the banks. Caimans, a kind of crocodile, sun themselves on the mud.
For many Venezuelans, the Orinoco is part of daily life. People in riverside villages travel by boat to school, to market and to visit family. Once a year the river floods huge areas of flat grassland, turning them into a sparkling shallow lake the size of a small country.