International Space Station

The International Space Station is the largest structure ever assembled in orbit, weighing over 400,000 kilograms and spanning the size of an American football field. Since November 2, 2000, it has hosted continuous human habitation, supporting more than 3,000 scientific experiments in microgravity research across medicine, materials science, and Earth observation. In terms of longevity, it outperforms every other habitable space outpost in history, remaining permanently crewed for over 25 years, which is 20% longer than the next most enduring orbital station. Its international collaboration, involving NASA, Roscosmos, ESA, JAXA, and CSA, sets a benchmark for multinational space cooperation that later missions like Cassini-Huygens have followed but not exceeded.