LONDON, April 15, 2008 -- Name a building and there is a good chance he has climbed it.
French climber Alain Robert, aka "The Spiderman," says he's scaled more than 80 buildings around the world.
That includes Chicago's Sears Tower -- his "most exciting climb," he told ABC News -- the Petronas Twin Towers in Kuala Lumpur, Malaysia, and the Eiffel Tower.
Today, Robert scaled Hong Kong's Four Seasons Hotel, a 45-story building and his third known climb in that city.
To succeed, he had to escape Hong Kong police, which had been tipped off about a possible illegal ascent in the city.
Police, emergency vehicles and large crowds flocked around the building to see the Frenchman climb the skyscraper barehanded.
"He's totally crazy. It's really dangerous," Jakob Mense, who saw the climb, told Reuters.
The Spiderman was shortly detained by police after the ascent and was released unconditionally, his lawyer told Reuters.
Robert used this ascent to promote greater awareness and international action on global warming.
"We are having to make the world understand that now we don't have any time in front of us and we need to act right away," Robert told reporters today.
Despite the enormous risks he takes during each climb, the 46-year-old has no intention of retiring .
"I am climbing bare hands," Robert told ABC News. "I am just using my climbing shoes, and I am using some chalk powder and that's it."
The Spiderman acquired his unique technique when he was 11. He had forgotten the keys to his apartment, and his parents were at work.
"I decided to climb the building," he said. "My parents lived on the seventh floor and I did it."
Robert remembers being a shy child. "I was lacking confidence," he said.
This original climb freed him from his inhibitions and made him resemble one of his "heroes," like Zorro or Robin Hood, he said.
"Finally, I was completely on the opposite side. That day I decided that I was going to change my life."
It's hard to believe when you see him stop at the 20th floor of a London skyscraper to sip a cup of tea and wave at the crowds below him, but the Spiderman says he used to suffer from acrophobia.
"I was afraid of heights," he said, "so it means that I have turned my biggest enemy into my best friend."
As to why he does it: not for the money, Robert said.
"I am doing it for the thrill, for that feeling of danger and freedom," he said. "This is my way of expressing myself."
In today's security camera-filled world, where one can be caught on film more than 100 times a day just walking the streets of London, Robert said that he wants to show the world that he is a free man.
"Whenever I am in London," he said, "I think that's a pity to have so many cameras above my head. Everything is too much based on security, and of course, against freedom."
For the Spiderman, being free also means refusing to climb a building when he does not believe the conditions are right.
"Many times, I have decided that I was not going to climb a building, just because the weather wasn't good, or simply because I didn't feel like doing so."
For him, climbing is all about calculated risks. He says the most important thing is to stay free but alive.
"Reaching the top of a building," he said, "it's a great feeling, because you are having that feeling that you have achieved something. You have realized a dream, and then, you can pinch yourself, [and say] f-- I am still alive."