Assembly at 28,000 km/h

The ISS was never launched in one piece. It was bolted together in orbit over 13 years, across 42 launches and more than 160 spacewalks. Each module flew up separately, then crews caught it, lined it up, and connected it by hand while floating in vacuum at 28,000 km/h — the speed of a rifle bullet, sustained for years.

It has been lived in without a break since November 2000. No human born this century has spent a single day in a world with nobody in orbit. At an estimated $150 billion, it is the most expensive object people have ever built.