Sima Martel and Sima Humboldt are two huge sinkholes that were discovered in 1961. They are located on the Sarisarinama Tepui, a remote 2,500-meter tall flat-topped mountain already known to host unique species. The larger of the two, Sima Humboldt, is so large that it has its own ecosystem at the bottom. Local legends describe them as mystical and evil places. This sinkhole is a lost world embedded into another. | Unsolved Mysteries & Paranormal Activities

295K views · 1.8K reactions | Episode 1 of Unsolved Mysteries looks into the baffling death of Ray Rivera. It's streaming now, along with five other episodes. | Netflix | Facebook

Unsolved Mysteries is back on July 1 Fusing signature elements from the original series with contemporary immersive, character-driven storytelling, the new episodes offer clues and theories with the hope that one viewer holds the key to solving the mystery. | Netflix