What on Earth? Season 12: Episode Guide & Ratings

Satellite capture a bizarre pattern obscuring an eastern Atlantic island.

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 large compound of abandoned structures that are overgrown with vegetation in Indiana; experts investigate and uncover a derelict WWII munitions factory that played a crucial role in US military history.

Aerial drone imaging captures a circular man-made structure that appears to be centuries-old in the remote forests of Aydin, Turkey; experts investigate a lost ancient amphitheater with a history steeped in gladiatorial bloodshed.

Satellite images capture a mysterious fortification concealed beneath a patch of woodland in the remote stretches of Norfolk, England; experts investigate rival royal families and a lost castle that was destroyed during a medieval blood feud.

Satellite images capture miles of aircraft precisely arranged in the vast Arizona desert; experts investigate the largest aircraft storage facility on Earth and the rotting remains of a defining moment in Cold War history.

Satellite images capture an enormous X shape mysteriously carved with precision in the remote Nevada desert; experts investigate a military emergency landing field linked to one of the most astonishing test programs in aviation history.

Satellite images reveal a mysterious vessel that suddenly appears marooned on a remote stretch of Ireland's southern coast; experts investigate and uncover a bizarre journey near the Bermuda Triangle that resulted in a US Coast Guard interception.

Satellite images capture a mysterious group of pyramid-shaped structures in the arid, desert landscape of Arizona; experts investigate a highly controversial research facility designed to prepare humanity for life on another world.

Aerial archaeologists capture a series of mysterious dots buried beneath the remote, frozen landscape of Finnmark, Norway; experts investigate and reveal revolutionary hunting techniques developed by the oldest surviving Norwegian tribe.