A boulder is a large rock that has been naturally shaped by weathering and erosion. Typically, boulders are defined as rocks that are at least 10 inches in diameter, but they can be much larger. They can be found in various environments, such as mountains, riverbeds, and beaches, and are often made of different types of rock, including granite, limestone, and basalt. Boulders can vary in size, shape, and color, depending on their geological origin. They play an important role in ecosystems by providing habitats for various plants and animals. Additionally, boulders are often used in landscaping and construction, serving as decorative elements or structural supports in projects like retaining walls and garden features.