Inside the abandoned Edinburgh tunnel stretching right under the city centre
Images found online have shown inside the Scotland Street Tunnel, which has lain empty since the early '80s.
Work began on the structure in the early 1840s, which would forge a link between Canal Street Station (now known as Waverley) and the north of Edinburgh. It would run underneath Scotland Street, Dublin Street and St Andrew Square.
Urban explorer James Perry filmed his trip into the tunnel, which is never advised, and uploaded the experience to YouTube. In the footage, we see the now derelict passageway which once saw thousands of passengers a day travel from one end of the city to the other.
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Costing over £100,000, it opened in May 1847. Rail services then travelled between Waverley and Granton, hauled by a steel rope and winding engine due to the sharp incline.
It was highly difficult to construct, and cost a lot of money, but was abandoned by the rail service after just 21 years. The North British Railway company found a more efficient way of transporting passengers to the north of the city.
Soon after, an unlikely operation moved into the tunnel. The Scottish Mushroom Company moved in, and used one side of the tracks to set up 800 mushroom beds - each 12ft by 3ft.
According to records their output reached up to 500lbs in one day, and produce was on offer during all seasons. This continued until 1929, when a parasite infection led to bankruptcy.
By the time of the Second World War, a new purpose was found for the tunnel. The city needed suitable hubs in the event of an air raid attack, and a shelter was set up.
Capable of housing up to 3,000 people, the tunnel became Edinburgh's largest and 'most safe' bomb shelter. Sitting 50ft below street level, it was considered an ideal spot to wait out an attack.
Since the war, the space has gone mostly unused - apart from a few odd spells. In the late '40s, the University of Edinburgh attempted a series of radiation experiments down there.
In the '60s, Cochrane Garages stored up to 150 vehicles in the tunnel. It didn't take long for youths to make their way into the tunnel and start a fire, which caused severe damage.
The southern entrance was demolished to make way for the Waverley Market in 1983, and the hopes of breathing new life into the Scotland Street Tunnel crumbled along with it. The northern entrance can be seen today - though is fenced off to the public.
Some have suggested transforming the derelict site into an underground car park, though nothing has been done yet.
The tunnel will likely never return to its rail days, but Robert Louis Stevenson's description of it in his travel book Edinburgh: Picturesque Notes paints quite a picture.
He writes: "The Scotland Street Station, the sight of the train shooting out of its dark maw with two guards upon the brake, the thought of its length and the many ponderous edifices and thoroughfares above, were certainly things of paramount impressiveness to a young mind."