Modern Edinburgh is a thriving cultural metropolis at the heart of the United Kingdom. From the Forth Railway Bridge to Edinburgh Castle, the city houses a wealth of impressive attractions and monuments. Yet there are countless subterranean secrets concealed beneath the picturesque streets of the Scottish capital.

In this fascinating instalment of ‘Cities of the Underworld’, we delve into Edinburgh’s double life. Above ground, Edinburgh has long been a sophisticated and educated city. Today, it is famed for a world renowned annual arts festival surface, as well as a rich literary tradition dating back to the Scottish Enlightenment.

Yet while Edinburgh cemented its reputation as Scotland’s intellectual and cultural hub, a darker world expanded below. From plague victims being buried alive under the streets to body snatchers, illegal distilleries and castle dungeons, Edinburgh’s underground has myriad mystifying tales to tell. We join Eric Geller as he investigates these stories, separating tartan truth from Caledonian conjecture. He discovers the engineering marvel of Edinburgh's underground, which was created when the city actually changed its street level.

Eric takes viewers on a gripping journey through a metropolis whose very existence was forgotten until recently. For almost 200 years, Edinburgh was surrounded by a giant defensive wall. Unable to expand its boundaries, it became the most densely populated city in Europe. The towering tenements of the Royal Mile are a direct physical manifestation of this massive overpopulation.

When the city buildings could not get any higher, people were forced to construct new edifices over the existing urban structures. After 1780 Edinburgh spread out from the crowded Royal Mile across the valley to the south, carried by the huge South Bridge. The bridge was built against almost immediately. As its nineteen enormous arches were closed off, a honeycomb of underground chambers were created. A community of traders, immigrants and homeless people thrived in this underground environment, yet criminals, black market traders, prostitutes, and the murderous and depraved soon infiltrated this troglodyte society.

Mired in a desperate morass of poverty and crime, these subterranean dwellers lived in darkness and misery for over 350 years, ignored by chroniclers of the time. By the 1830s, the underground vaults had been abandoned. Edinburgh’s population came to believe that the underground city, out of sight and out of mind since its abandonment in the nineteenth century, had never been there at all. Yet the vaults were rediscovered in the mid 1980s, and opened to the public in 1994. This programme comprehensively chronicles Edinburgh’s gripping subterranean history.