Lake Marathon is a large reservoir located in Marathon, a town on the island of Evia in Greece. It was constructed between 1926 and 1931 to supply water to Athens and is known for its scenic beauty and surrounding natural landscape. The lake is fed by the Marathon River and plays a crucial role in the region's water management. The lake is also a popular spot for outdoor activities such as hiking and birdwatching. Its dam, the Marathon Dam, is an important engineering structure that helps regulate water flow. Lake Marathon is not only vital for water supply but also serves as a recreational area for locals and tourists alike.