Yishun Dam, also known as Seletar Dam, is a roadway in Singapore that spans the Seletar Reservoir, connecting the northeastern parts of Singapore to the central and western parts of the island. The area surrounding the dam is known for its scenic beauty and is a popular spot for outdoor activities like fishing, cycling, and photography.

The dam was built as part of the construction of the Seletar Reservoir, which is now known as the Upper Seletar Reservoir. The reservoir was built to meet the increasing demand for water in Singapore. The dam serves the practical purpose of separating the fresh water of the reservoir from the seawater, effectively creating a freshwater source for the city-state.

The construction of the Seletar Reservoir started in 1920 and it was officially opened by Her Royal Highness, Princess Alexandra in August 1969. The reservoir, along with its dam, represented a major feat of engineering at the time and continues to serve a critical role in Singapore's water supply system.

Apart from its practical function, Yishun Dam also serves as a scenic viewpoint. With panoramic views of the reservoir on one side and the sea on the other, the dam has become a popular destination for locals and tourists alike, especially at sunset. The area also has a rich biodiversity, attracting bird watchers and nature enthusiasts.

To sum up, Yishun Dam was primarily built as a crucial part of Singapore's water management infrastructure, aiding in the creation of the Upper Seletar Reservoir. Over time, it has also become a significant recreational and scenic spot in Singapore.