What is the rarest river ever?

Answer 1

The rarest river is often considered to be the River Thames in London, particularly noted for its unique tidal characteristics and historical significance. However, if we refer to rarity in terms of its ecological or geological features, rivers like the Rio Tinto in Spain, which is known for its striking red color due to high acidity and metal content, could also be classified as rare. Additionally, the Black River in Jamaica, with its unique blackwater ecosystem, showcases the diversity of rare river types.