Eric Geller reveals Istanbul's hidden history.

Edinburgh, Scotland is a thriving metropolis in the heart of the United Kingdom. But take a look into its past, and you'll find it has led a double life - the sophisticated and educated surface city blossomed above while a darker, seedy world expanded below. From plague victims getting buried alive under the streets to body snatchers, illegal distilleries and castle dungeons, Edinburgh's underground has many stories to tell. Host Eric Geller investigates these stories, deciphering fact from fiction, while uncovering the engineering marvel of Edinburgh's underground - created when the city actually changed its street level. We're peeling back the layers of time on Cities of the Underworld: Scotland's Sin City.

Berlin, Germany was the battlefield of the 20th century. And today, sealed up and forgotten beneath its streets are remnants of this dark past. Walk anywhere in the city and you could be walking directly on top of one of the over 1000 Nazi bunkers engineered into Berlin's sandy soil, lost remnants of Hitler's ill-fated Germania or even beer brewing plants that inspired the Nazis' journey into the underground. Join host Eric Geller as he travels through the dark and damp recesses of Berlin's secretive soil. We're peeling back the layers of time on Cities of the Underworld: Hitler's Underground Lair.

Rome, Italy is a city where the past meets the present on every street, and below them. Caesar. Augustus. Nero. Rome has had some of the most infamous rulers, and each one of them has left their mark on the city - and left remnants of his reign underground. A secret cult practiced right next to the Circus Maximus, and their temple still remains beneath the street. The famous Piazza Navona sits on top of Domitian's Stadium. Pieces of Trajan's Basilica can be found under a gallery owned by fashion dynasty, Fendi. Rome's underground is filled with evidence of life during the Empire. Join host Eric Geller as he discovers what life was like during Nero's tyranny and Augustus' reforms. We're peeling back the layers of time on Cities of the Underworld: Rome's Hidden Empire.

Paris, France is Europe's famous "City of Lights," but an alternate world thrives in the shadows of this capital city. Crypts filled with the bones of former residents, ancient waterfronts, waste-filled sewers, and hundreds of miles of limestone tunnels snake beneath Paris' charming neighborhoods and bustling streets. Host Eric Geller has special access to this dark underworld, where both the secrets of the living and the sins of the dead are revealed. We're peeling back the layers of time on Cities of the Underworld: Catacombs of Death.

Budapest, Hungary is a burgeoning Easter European metropolis sitting on top of an ancient secret - a secret that dates back to the dawn of time. The caves beneath Budapest were formed during the ice age and everyone from the cavemen to the communists have moved their city into the depths of this parallel world. Host Eric Geller has special access into this sealed up time capsule - where he'll uncover a top secret WWII hospital, find the source of the boiling healing water used by both the Romans and the Turks, and see the layers of support added throughout the centuries to keep today's world from falling into the one buried below. We're peeling back the layers of time on Cities of the Underworld: City of Caves.