The International Space Station continues to orbit the Earth and provide living and work space for a small number of astronauts, but it was not the first habitat to be built for orbit. Mir and Skylab were the first two space habitats to be constructed. Like the ISS, both were built on Earth and shipped up to orbit. The ISS went one step further by adding modules over the years. Future space stations may be built entirely in space rather than launched from the planet's surface.
All three space habitats have been learning projects for engineers and builders of the future. There are different factors that must be accommodated to live in this harsh environment. New and stronger materials will be found when mankind finally builds a rotating space station to provide artificial gravity to the residents. Each new venture into space provides builders with data to help them design and built space cities in the centuries ahead.