The International Space Station (ISS) is a spacecraft large enough for several astronauts to live on at once. It orbits the Earth 400 km above our planet's surface, travelling at 27,600 km/hour. This means it completes 1 orbit of the Earth in 90 minutes! You can sometimes see the ISS at night - you don't need a telescope. It looks like a small, bright dot moving quickly across the sky.