The Thémis power plant, a solar thermal tower power plant located in Targasonne, France, was built in 1983 with the goal of proving that solar energy could be used to generate electricity instead of oil. The plant had 201 adjustable mirrors and a 101.5-meter-high tower, which could produce 2.5 megawatts of electricity. The mirrors focused sunlight onto a receiver at the top of the tower, where molten salts were heated to create steam, which then powered a turbine. The location was chosen for its good weather, with nearly 2,400 hours of sunshine per year and light winds that minimized the risk of production interruptions. The plant operated for three years before being shut down in 1986. Some reports say the closure was due to the sudden drop in oil prices, which made solar energy more expensive in comparison. Other sources suggest that the decision was more about ending research on solar power than economic factors. In 1986, EDF, the French electricity company that had funded the project, withdrew its support. The high repair costs, low electricity output, and high cost per unit of energy made the project unsustainable when oil became cheap again. Despite its closure, the technology developed at Thémis found success in other countries, especially Spain and the United States, where solar concentration power plants became more common in the decades that followed. However, the Targasonne site remained largely unused until 1987, when it was taken over by astrophysicists for a new purpose: detecting cosmic gamma radiation. The CNRS, along with IN2P3, CEA, and CERN, used the site to study high-energy gamma rays from space, hosting several telescopes over the years, including Thémistocle, ASGAT, CAT, and finally Céleste. The mirrors originally designed to capture sunlight were repurposed to observe the night sky, becoming part of a giant Čerenkov telescope used to detect cosmic rays. This second use ended in 2004, when the researchers moved to South Africa, where they found a more suitable location for their work. The Pyrénées-Orientales Department, which owned the site, then decided to revive the original purpose of Thémis. In the same year, the site was redeveloped under the name Thémis Solaire Innovation, aiming to become an international hub for research and innovation in concentrated solar power. Twenty-one years after its abrupt shutdown, the Targasonne site is slowly returning to its original mission. Of the 201 mirrors installed in 1983, only 195 are still fully functional today, with the other six removed for use in astrophysical experiments.