An investigation has been launched after a man suffered injuries after falling from the roof of the Winter Gardens.
Video footage shows the man hanging by his arms from metal girders above the Floral Hall at the venue which was hosting the annual Magicians Convention.
The incident happened shortly after midnight on Sunday.
One witness, Arron Jones, a 23-year-old magician from Sheffield, said the incident happened just minutes after the final show of the night had ended.
He said: “I think he was trying to prove he could get from one side to the other, and he just slipped.”
Mr Jones was enjoying a drink in the main foyer with a friend when he said the man shimmied up a palm tree and began climbing up the wall.
He added: “I had a very visceral reaction and screamed the loudest.
“We thought we had just seen a man die because of the height and the sound he made hitting the floor.”
He said he believed the man was a member of the audience and not part of the show.
Michael Williams, managing director of the Winter Gardens, said: “There is an investigation ongoing into the circumstances being carried out by the Winter Gardens with the Magicians Convention.
“If we need to, we will also consult with the Health and Safety Executive.”
A spokesman for Blackpool Magicians Convention declined to comment other than to say the event will be discussed at its next meeting.
A spokeswoman for the North West Ambulance Service (NWAS) said a rapid response car and ambulance were called to the historic venue at 12.26am on Sunday.
She said the man, in his 20s, was taken to Royal Preston Hospital with hip and shoulder injuries, as well as a suspected head wound.
The four-day convention, staged by Blackpool Magicians Club, is the largest annual magic convention in the world.
It has been held at the Winter Gardens for 65 years.
More than 3,500 fellow magicians and music enthusiasts were expected to attend this year’s event, from as far a field as China and USA.
The convention also showcased more than 100 magic dealers, world-class close-up magicians, lecturers and stage performers.