Science Channel HD

A breathtaking stainless steel tower seems otherworldly and out of place in the remote mountain forests of Croatia; experts investigate and uncover a dark past of Nazi-led conflict and a monument to a desperate fight for survival.

Long, dome-like structures camouflaged by a rural landscape conceal the remains of concrete vaults with a hidden history; experts investigate and uncover state-of-the-art bunkers built to conceal and protect a deadly nuclear secret.

Atlantis is one of the most famous disappearances of all time; after thousands of years, state-of-the-art technology might finally be able to crack this ancient mystery; after nine hikers die in a gruesome cold case, new science provides a hot lead.

The Roanoke colony vanishes without a trace, and centuries later, it remains one of history's greatest unsolved mysteries; but new evidence might at last reveal its fate; after a man is swallowed by earth, experts wonder if a sinkhole is to blame.

Counting down the most epic fails with the internet's ultimate mistake makers; these clips are an instruction manual in failure; a crash at 300 mph; a person freaks out in virtual reality; a jetpack goes catastrophically wrong.

Soviet photos of the moon are intercepted by the CIA; a malfunction aboard the ISS, which imperils the whole crew; NASA probe finds evidence of the possibility of life on Mars.

A declassified letter written by President Kennedy demands that the CIA share its UFO data with NASA; a bizarre pattern on the surface of Mars could be a coded alien message; investigators find a rocket crash-landed in a crater on the Moon.

Supernovas are the violent death of giant stars, and new discoveries reveal that these cataclysmic events create the elements that are essential to all life in the universe.

Cosmic rays capable of destroying human DNA are hurtling through outer space like subatomic bullets, causing space crews radiation damage.

A hidden, subterranean city built within the Rock of Gibraltar is an immense fortress to control the seas during World War II; new discoveries reveal the secrets of a long-lost chamber with evidence of high-stakes espionage.

A mysterious cave system is home to some of the oldest human remains ever discovered, and today, the explorers and researchers investigating this site are uncovering shocking evidence of cannibalism among its Ice Age denizens.

A strange, centuries-old labyrinth built into an abandoned quarry was built by an eccentric millionaire, and no one knows why; but now, a new excavation into this mysterious 9,000-foot tunnel system might finally reveal its dark secrets.

A strange underground system known as the Black Cave is connected to a fairytale castle and was home to an infamous nobleman on the run from the law; experts investigate the secrets he left here to discover new parts of this mysterious network.

A labyrinth of vast tunnels in the French countryside has served as a secret hideout during wartime for centuries, and on its walls, experts have discovered the final confessions of soldiers who fought during one of the deadliest days of World War I.

A buried ancient city hidden five-stories underground can house 3,000 people in secret; experts use the latest tech to reveal the truth behind this strange place.

A vast system of tunnels built almost 3,000 years ago was the site of the greatest battles of antiquity, and these disorienting passages could be the deadliest weapon in war; experts reveal what made this underground world so terrifying.

Satellite images capture a bizarre pattern of enormous circular clouds obscuring an island in the eastern Atlantic; experts investigate and uncover evidence of an unfolding natural disaster that could potentially threaten millions of lives.

Aerial drone imaging captures clusters of enormous, perfectly round holes scattered along the coast of the Dead Sea in Israel; experts reveal a history of destructive water diversion linked to massive sinkholes devouring the region.

Aerial drone imaging captures oddly shaped industrial-sized towers mysteriously situated in a forest clearing near Moscow; experts investigate a lost Soviet era military compound and the development of a catastrophic electromagnetic weapon.

Aerial archaeologists capture bizarre, spider-like markings etched deep into the mountains of Northern Spain; experts investigate an ancient site that contained one of the largest and most important gold mining operations of the Roman Empire.

Aerial archaeologists use laser imaging to capture a distinct star-shaped pattern carved into the marsh of a Florida swamp; experts investigate and reveal a lost Civil War fort linked to an extraordinary community with a tragic past.

Satellite images capture a series of enormous zigzagging patterns carved into the remote woodlands of Poland; experts investigate a clandestine Nazi base linked to a doomed operation that played a pivotal role in the downfall of WWII Germany.

Aerial archaeologists capture bizarre, spider-like markings etched deep into the mountains of Northern Spain; experts investigate an ancient site that contained one of the largest and most important gold mining operations of the Roman Empire.