In the Rance estuary, located between the French towns of Dinard and Saint-Malo, a tidal power plant has been in operation since 1966. This facility uses the natural rise and fall of ocean tides to generate electricity. A 750-meter-long dam blocks the mouth of the Rance River, and beneath the road that connects the two sides of the estuary, 24 turbines harness the energy of the tides. These turbines, known as Kaplan turbines, are capable of producing power both when the tide is rising and when it is falling. The plant, inaugurated by former French President Charles de Gaulle, was the world's first tidal power station and remained the largest of its kind for many years. It has an installed capacity of 240 megawatts and produces about 500 gigawatt-hours of electricity annually—enough to power a medium-sized city without emitting carbon dioxide. The concept of building a tidal power plant on the Rance dates back to 1921, with serious planning beginning in 1943. The project was officially approved in 1959 and constructed from 1961 to 1966. The Rance estuary was selected due to its exceptionally high tidal range of 13.5 meters, among the highest in the world. Construction required the estuary to be completely drained for three years, from 1963 to 1966, which had significant environmental consequences. Some aquatic species, like the lançon and the plie, disappeared, while others, such as the bar and the seiche, adapted to the new conditions. Additionally, the dam has led to increased sediment buildup, with annual deposition rates increasing from 30,000 to 50,000 cubic meters in 2003 to 300,000 to 500,000 cubic meters per year by 2019. A common seal has also been spotted in the area since 2001, likely having crossed the dam through the lock system. To ensure the plant continues to function efficiently, the energy company EDF has launched a renovation program that includes a 100 million euro investment over ten years, aiming to extend the plant's operational life until 2025. Part of the 24 turbine groups will be upgraded as part of this effort. The dam also serves a dual purpose as a road bridge connecting Dinard and Saint-Malo, a fact that many visitors might not realize when they cross it. The transformation of the Rance estuary continues, with more mudflats forming and species adapting to the changing environment. What was once a natural river has become a complex system that generates clean energy while reshaping the local ecosystem.