An industrial facility designed to safely store hazardous nuclear waste for far longer than human civilization is the focus of the Cigéo project, a geological storage center planned by France’s National Agency for Radioactive Waste Management (Andra) near the border of the Meuse and Haute-Marne departments. The plan involves digging underground galleries 500 meters deep into a specific layer of clay known as Bure clay, which is more than 160 million years old. This clay is chosen for its unique properties—its minerals can swell and seal cracks when exposed to moisture, reducing water flow and slowing the movement of radioactive materials. This natural process could potentially isolate the waste for hundreds of thousands of years. The estimated cost of the Cigéo project is 33.4 billion euros, based on economic conditions from 2025. Earlier projections ranged from 25 billion euros in 2011 to as high as 37.5 billion euros in 2025, depending on various assumptions. The project was launched in 1991 but is still in the administrative instruction phase. If approved, construction and operation could span more than a century. The site is designed to remain safe even without active human monitoring after it is completed. A key principle of the Cigéo project is reversibility, which requires the facility to be reopenable for at least 100 years. However, some scientists question whether it would be feasible to reopen the site centuries after it has been sealed. Another challenge is warning future generations about the buried danger. To address this, the "Memory for Future Generations" program proposes using durable markers with universal pictograms and multilingual messages to communicate the site's existence and its risks over tens of thousands of years. In 2022, the Cigéo project reached a symbolic milestone with its declaration of public utility, and an application for authorization was submitted to the technical safety authorities. The approval process is still ongoing, with several regulatory steps remaining before a final decision is made. The project continues to spark debate in the Meuse and Haute-Marne departments, where concerns about its long-term safety and viability remain.