The Irrawaddy starts high up in the Himalayan foothills, where two icy mountain streams meet. From there it grows wider and slower as it travels south. By the time it reaches Bagan and then the southern delta, the river is several kilometres wide in places.
More than 30 million people live near the Irrawaddy. The river waters their rice fields, feeds them fish, carries their boats and connects their cities. Big wooden cargo boats - low and flat - chug up and down with bags of rice, oranges and pottery. In some villages, the river is still the main 'road'.
Down at the southern end, the Irrawaddy splits into many smaller channels that fan out into the sea. This is called a 'delta'. The delta is made of soft, rich soil washed down from the mountains - perfect for growing rice. Most of the rice Myanmar eats comes from this one corner of the country.
The river has been the country's main highway for thousands of years. The old kings of Bagan and Mandalay travelled up and down it in great gilded barges. Today, families catching the dawn ferry past temple-dotted banks still see roughly the same view those kings did.