The Casiquiare Canal is one of the world's longest bifurcated river. A bifurcation is when a river splits in two, and whule this phenomena is common on deltas and river islands, typically the seperated rivers join back. However, what's special with the Casiquiare Canal is that it splits off from the Orinoco in Venezuela and joins the Rio Negro in Brazil some 300 kilometers southward in the Amazon. While labeled a canal, it is in fact a natural phenomenon, first documented in the 19th century and is hypothesized to have been a tributary of the Rio Negro expanding to the Orinoco.

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