Amazing statistics about the Amazon river

"Vastly bigger than any river in Europe or Asia, the Amazon contains a fifth of the earth's above-ground fresh water. It has islands the size of countries and masses of floating vegetation the size of islands. Half a dozen of its tributaries would be world-famous rivers anywhere else. A thousand miles up from the Atlantic, the river is still so broad that at high water the other side is only a faint dark line on the horizon. Ferries take half an hour to make the crossing. Seagoing vessels travel all the way up to Iquitos, Peru, 2,300 miles from the river's mouth, the furthest inland deep-ocean port in the world...
Like today's ecotourism brochures, the accounts of the great river basin in da Cunha's time celebrated its immensity but rarely dwelled on its extreme flatness - in the Amazon's first [last?] 2,900 miles the vertical drop is only 500 feet."
Citations from this book.