A mysterious herb called silphium was widely used by the ancient Greeks and Romans in cooking, medicine, and even as a form of birth control. Some people think that our "heart" shape ❤️ is based on the shape of its seeds. The exact identity of silphium is unknown, but it likely went extinct sometime in the first century AD.
in the entire river!
its huge that's crazy
Manaus comes very close though, with a bridge just a couple of kilometres away crossing the Rio Negro tributary.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8857275/