International Space Station
1998-present
The largest structure humans have ever built. Continuously crewed since November 2000, assembled in orbit from 40+ pieces by Shuttle and Russian rockets.
Specs
~410 t; 109 m long; ~420 km orbit; 7.66 km/s (27,600 km/h); one lap of Earth every 92.9 min; 15 partner countries.
Why it matters
It was assembled, not appeared: Zarya launched 20 Nov 1998, the US node Unity mated to it sixteen days later by Shuttle Endeavour's robotic arm, and 37 Shuttle visits followed over thirteen assembly years - every launch tracked by radar worldwide. It has been continuously crewed since 2 Nov 2000; more than 270 visitors from about 20 countries. And it is still an engineering site: its orbit decays from drag and needs re-boosting on a published schedule, it is a naked-eye dot brighter than any planet whose passes you can predict from free orbital data, and spacewalks still run its wiring - the debunk card iss-hoax walks through what that makes the 'it is faked' claim require.