This is a documentary fom the BBC. I am embedding it here as an introduction to a fascinating story.
Click on the triangular PLAY button on the lower left below the picture itself.
Note: If your browser does not show an image above this text, particularly if you are using some versions of Safari, click here and it will take you to the the video.
To give some perspective on the scale and location of terra preta sites, here is a link to a map of sites.