Ally Law and friend Adam Marr snuck on to the observation tower before ascending around 400ft to the top, offering astounding, albeit queasy, views of Glasgow.
The structure was built in 2001 but has been shut for about two thirds of its lifespan, re-opening to the general public in 2014.
Law, from Southampton, was unaware of the building even though his father's side of the family are from the city before people suggested it as his next climb.
"It was actually an easy climb but doing it with my backpack proved to be difficult as I had about 20kgs of equipment in there," said the 20-year-old.
The video has been watched more than 43,000 times.
The duo "began through parkour, jumping from small rooftops to rooftops and just progressed into this really".
Law has climbed all over the world, from Dubai to Australia to Hong Kong. Recently he and a group of friends climbed into Manchester City’s Etihad Stadium and on to the roof before armed police came on scene.