The ITER Fusion Reactor: The World's Most Complex Construction Project

Wikipedia:

ITER (initially the International Thermonuclear Experimental Reactor, iter meaning "the way" or "the path" in Latin) is an international nuclear fusion research and engineering megaproject aimed at creating energy through a fusion process similar to that of the Sun. It is being built next to the Cadarache facility in southern France. Upon completion of construction of the main reactor and first plasma, planned for 2033–2034, ITER will be the largest of more than 100 fusion reactors built since the 1950s, with six times the plasma volume of JT-60SA in Japan, the largest tokamak operating today.

The long-term goal of fusion research is to generate electricity. ITER's stated purpose is scientific research, and technological demonstration of a large fusion reactor, without electricity generation. ITER's goals are to achieve enough fusion to produce 10 times as much thermal output power as thermal power absorbed by the plasma for short time periods; to demonstrate and test technologies that would be needed to operate a fusion power plant including cryogenics, heating, control and diagnostics systems, and remote maintenance; to achieve and learn from a burning plasma; to test tritium breeding; and to demonstrate the safety of a fusion plant.