The International Space Station is the largest structure ever built in space.

The first module — the Russian Zarya module — launched from Earth 15 years ago on Nov. 20 1998. International crews have continuously occupied the orbiting space laboratory since 2000, and five space agencies contributed to the building of the structure. [Cosmic Quiz: Do You Know the International Space Station?]

The $100 billion International Space Station has the wingspan of a football field and the living space of a five-bedroom house. It took more than 115 spaceflights of different kinds of spacecraft to build the station, and astronauts and cosmonauts have spent more than 1,000 hours on spacewalks outside of the station.