Crowds watched as the 21-year-old British free climber made his way to the top of the 116-meter (381 ft) Melia Barcelona Sky Hotel in the Spanish city.
As he was coming down, he was arrested by the Mossos d'Esquadra, the Catalan regional police and faces a fine.
"When I was at the top I felt that I was in another dimension of bliss," King told Reuters. "When I met the police on the way down my head was still in the clouds."
King scaled the Barcelona hotel in about 20 minutes. He first climbed the 310-meter (1,017 ft) The Shard building in London in 2019, the highest tower in the United Kingdom, without any safety apparatus.
The feat earned him six months in a young offenders' center for breaching a civil injunction taken out by the owners of the building.King, from Oxford in England but currently traveling around Europe in a van, has also climbed the 144-meter (474 ft) Agbar Tower skyscraper in Barcelona.