Police are investigating footage which shows a teenager climbing to the top of Birmingham's iconic Selfridges building.
He is also filmed climbing along steel support wires which connect to the bridge link running between the building and the car park opposite.
Friends watching from the street below filmed his free-climbing Spider-man exploits, which were yesterday labelled "extremely dangerous" by police.
After climbing back to the ground, the teenager is filmed bragging about the feat and telling friends how treacherous it was.
The footage, from someone calling themselves Bozzys TWIO, was posted on YouTube, but has since been removed.
Police were later called in after details were forwarded to BRMB radio station. Yesterday, they warned copycats would be arrested.
Confirming they are investigating, a West Midlands Police spokesman said: "We would urge people not to take part in this extremely dangerous act. Not only is it putting themselves at risk but if caught they could face arrest and possible criminal charges."
According to their posting on the website, the group behind the stunt call themselves TWIO which stands for 'The World Is Ours'.
They say they are a group that will "do anything to make the world theirs" and "whatever they can for fun, and to get a good buzz".