Two Russian men illegally entered the construction site of Shanghai Tower and climbed to the top of China's tallest building during the Spring Festival holiday, according to a video that went viral online on Thursday.

Vadim Makhorov and Vitaliy Raskalov filmed themselves wearing head-mounted cameras as they climbed over a wall to the construction site and hiked to the top of the 632-meter-tall Shanghai Tower, which will be the second-tallest building in the world after it is completed later this year.

The five-minute video shows the two climbing up a crane atop building without any safety equipment. They reached a height of 650 meters.

Photos showing the two sitting on top of the crane and dangling their feet above the clouds amazed many netizens.

Raskalov revealed in his blog that they arrived at the construction site around midnight, spent two hours walking to the skyscraper's 120th floor and waited for hours to get a beautiful view.

Last March, the pair dodged guards and climbed to the top of Pyramids at Giza, Egypt, and took spectacular photos.

A spokesman for the Shanghai Tower, surnamed Zhu, said people are prohibited from climbing to the top of the tower without permission.

"The construction was suspended and most workers left during Spring Festival," she said.

In 2007, French veteran high-rise climber, Alain Robert, was detained by Shanghai police for five days and ordered to leave the country for climbing the Jin Mao Tower, another skyscraper in the city’s financial hub Lujiazui.