STORY: Julien Robert joined his father to climb the 470-ft Torre Glories, formerly the Torre Agbar, a glass-fronted office building famed for its nighttime illuminations.
Alain Robert, 60, told Reuters before the climb that "This time is different. My son is not a climber, so I feel responsible somehow."
Julien, who spent eight years in the army, said he had never been so afraid for his life.
They completed the climb in less than an hour and were met at the top by police, who escorted them down the more traditional way - inside the building.
Robert rarely gets permission and climbs without a harness, using only his bare hands, a pair of climbing shoes, and a bag of powdered chalk.