Police have arrested self-described French Spider-Man Alain Roberts after he stopped traffic at the corner of a busy Sydney street by climbing one of the city's skyscrapers.

A crowd of about 200 people gathered at the corner of Phillip and Bent streets as Roberts climbed the 41 level RBS Tower at Aurora Place.

The crowd cheered when he reached the top of the building and immediately began his descent to street level.

Police had closed off a section of Bent St between Phillip and Macquarie streets and had officers ready to arrest Roberts.

He was duly arrested when he finished his descent, to more cheers from the crowd.

Roberts has scaled more than 70 skyscrapers all over the world including Chicago's Sears Tower, Canary Wharf in London and the Petronas towers in Malaysia.

Peta, an office worker who stopped to watch as she was buying a coffee after a morning meeting, said it was fantastic that Roberts was climbing the building.

"I think it's is really important for people to push the limit, I think it's an important part of life, going out and doing crazy things," she said.

"It's absolutely ridiculous, it's great. I love it."