Answer: As of my last knowledge update in September 2021, the largest construction project in the history of mankind was the International Space Station (ISS). While it may not be a traditional construction project on Earth, it was an enormous and complex endeavor involving multiple nations and space agencies. The ISS is an orbiting space laboratory that has been continuously inhabited by astronauts and cosmonauts from various countries since the year 2000. It required numerous space shuttle missions, Russian Soyuz and Progress spacecraft, and contributions from multiple international partners, including the United States, Russia, Europe, Japan, and Canada.