The most striking Hopewell sites contain earthworks in the form of squares, circles, and other geometric shapes. Many of these sites were built to a monumental scale, with earthen walls up to high outlining geometric figures more than across. Conical and loaf-shaped earthen mounds up to high are often found in association with the geometric earthworks. The people who built them had a detailed knowledge of the local soils, and they combined different types to provide the most stability to the works. It required the organized labor of thousands of man hours, as people carried the earth in handwoven baskets.