For years, Unsolved Mysteries has enthralled (and terrified) true-crime lovers with its accounts of gruesome murders, haunting disappearances and paranormal activity.

In news that will either excite or scare, the series has featured cases from Colorado over 40 times. While some episodes focus on fun anomalies like Bigfoot, others are more sinister, chronicling notorious serial killers like Ted Bundy.

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It's hard to say which cases are truly the most unsettling, but these will definitely have you double-checking your locks tonight. Here are some of the creepiest Colorado cold cases on Unsolved Mysteries:

Creepiest Colorado Cold Cases Featured on "Unsolved Mysteries"

Northern Colorado's Most Puzzling Cold Cases

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