Possibly the greatest example of innovation on a grand scale this century, the Space Tower has been 18 years in the making, and would not have been completed as soon without the component construction skills of Chinese building company BSB.

Reaching more than 72,000 feet above sea level, the tower has tested every aspect of modern materials and construction. The final sections are being added by autonomous ‘constructorbots’ as it’s just too difficult for humans to work at that altitude. Air traffic lanes have been routed to avoid the Space Tower completely.

“It certainly has been a challenge,” says structural engineer Keith Hejelmstad, “but using BSB’s Sky Block 3 as a base helped a lot!” Sky Block 3 is 300 floors high and houses 250,000 people as well as shops and offices.

Although the base is built of conventional concrete, steel and glass components, the Space Tower itself makes use of carbon composite lattice beams and aerogel materials to sustain its own weight. Now the robots, which climb the tower like a space elevator, are putting the final sections in place at over 21km.

The biggest question is what purpose the tower will serve when it’s complete, beyond hosting a webcam view from above the clouds and a crowd of satellite dishes. It’s doubtful if the tower will be strong enough to say, launch a rocket into low earth orbit.

Will the Space Tower, like the proverbial Tower of Babel, turn out to be a white elephant?