An abandoned gothic palace in Sintra, Portugal is home to an extraordinary structure with ties to the Knights Templar, in this clip from Season 3, "Secrets of Abandoned Places."

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From the producers of Ancient Aliens and The Curse of Oak Island comes The UnXplained, a one-hour, non-fiction series that explores the world's most fascinating, strange and inexplicable mysteries. Hosted and executive produced by Golden Globe and Emmy Award-winning actor William Shatner (Star Trek, Boston Legal) each episode will feature compelling contributions from scientists, historians, witnesses and experiencers-each seeking to shed light on how the seemingly impossible actually can happen.

The HISTORY Channel® is the leading destination for award-winning original series and specials that connect viewers with history in an informative, immersive, and entertaining manner across all platforms. The network's all-original programming slate features a roster of hit series, premium documentaries, and scripted event programming.