Behind a door deep within the lower floors of the National Library of Scotland lies a forgotten street that gives a glimpse of what Edinburgh looked like centuries ago.

Libberton’s Wynd, in the heart of the old town, was demolished to make way for George IV Bridge in the 1830s – but part of the street still stands.

It can be found between the walls of the bridge and the library building, accessed through a hidden door.

The corridor – named The Void by library staff – is not open to the public, but BBC Scotland News is allowed to see inside.

Library officials discovered it in the 1990s when they broke down a small essay on a wall behind a filing cabinet, and went through it.

They came upon an arched passageway into rooms and chambers that were thought to have once been storage in the bridge.

Bill Jackson, the library’s former director, told BBC Scotland News that he had found old rotting furniture, ledgers, shoes and a slate urinal that was more than 100 years old, but had been flooded and damaged.

“My torch was barely illuminating anything, it was very dark when I went through and a bit scary trying to get out of there.

“It was interesting though.”

Since then he has installed lights and another door at the Cowgate end of The Void.

The library rooms were built on top of the foundations, which can still be seen, of buildings demolished in Libberton’s Wynd to make way for George IV Bridge.

Robbie Mitchell, reference assistant at the library, said that inside the passage you could see the brickwork on the lower levels of the library and the stonework of the bridge.

“Although not a reformed street like Mary Stair’s Close, this gives us a glimpse of Edinburgh hundreds of years ago,” he said.

“There are a number of maps and accounts of the Old Town in the library’s collections which help us build an atmospheric picture of the neighborhood where George IV Bridge and the library now stand, and what it was before The Void.”

George IV Bridge was built as a way to connect the center of Edinburgh – the Royal Mile – over the Cowgate, which was in a valley, with the south side of the city.

There were rooms in the arches on several floors for storage for the shops at the top of the bridge.

Libberton’s Wynd was the route from Cowgate to Edinburgh’s gallows in a part of the Royal Mile known as The Lawnmarket – before it was demolished to make way for the bridge.

Later, the National Library of Scotland was built on top of the bridge, with floors running all the way down to the Wood Gate below.

The bridge was built on the foundations of Libberton Wynd, which can still be seen in The Void.

The trail runs for hundreds of feet on a steep gradient.

Officials have widened the entrance so there is now a full-sized door. Some of the rooms are now used to store huge water tanks for the library’s sprinkler system.

Mr Mitchell said large crowds, often many thousands, attended the executions at the city gallows where Wynd Libberton entered the Green Market.

One of the most famous people to be executed was the corpse-hanger and murderer William Burke in January 1829.

Libberton’s Wynd was also famous for the city’s most famous pub, known as The Mermaid before it became Johnnie Dowie’s Tavern.

Pubs were a key feature of Edinburgh’s Old Town communities, with patrons often drawn from different social classes.

John Dowie was described in the accounts as “the sleekest and kindest of landlords”. He always wore “a cocked hat, buckles on the knees and shoes, as well as a cross-arm cane, over which he bent his way”.

Mr Mitchell said the most popular drink was Edinburgh brewed and supplied by Archibald Younger.

This was described as “a strong fluid which stuck the lips of the drinker almost together, and few of them, therefore, could send more than a bottle”.

Mr Mitchell said descriptions of the pub, which was on the ground floor of a high-rise tenement, gave a sense of the claustrophobic confines of the Old Town.

About 14 people could sleep in his main room, which looked out onto the Wynd, but the other rooms were said to be so small that no more than six people could fit in each.

They were described as being “so dingy and dark that, even in broad daylight, they were lit up by artificial means”.

The Tavern was described as a house of “much respect” and was a popular meeting place for “the chief wits and men of letters” in Edinburgh.

Writers regularly attended including the poet Robert Fergusson, artists and many members of the judiciary.

The smallest of his windowless rooms was an irregular umbilical box commonly known as “the Coffin”, believed to be Robert Burns’ favorite seat in the Tavern.

Libberton’s Wynd was first mentioned in the late 15th Century, but was demolished by 1835.

Local historian Jamie Corstorphine said entering The Void was one of his most exciting experiences.

“The name of the wind probably came from Henry Libberton, who owned a large property on the wind – or if not, then his family, who remained in the house for many years after his death in 1501.

“There were merchants, barbers, cobblers, grocers, a custom house, fanners, cork cutters, silver turners, gossiers and glaziers in the street.

“It was a very busy street that would have been full of life at the time.”