International Space Station

The most expensive structure ever built ($150 billion), the ISS has been continuously occupied since November 2000 — over 25 years of unbroken human presence in space. A collaboration between 15 nations, it orbits at 28,000 km/h and has hosted over 270 astronauts from 21 countries. More than 3,000 scientific experiments have been conducted aboard, spanning biology, physics, medicine, and materials science. The ISS proved that rival nations could cooperate in space, even when they couldn't agree on anything else.