Arlington's Dark Star Park, competed in 1984, was the first major commissioned public art project in the County. It was designed by artist Nancy Holt, who is widely known for her large-scale environmental works that often deal with issues of how people perceive time and space. Her designs blend with and complement their environment, and are harmonious with the land. Dark Star Park, which replaced a run-down gas station and warehouse, consists of five spheres, two pools, four steel poles, a stairway, a large tunnel for passage, a small tunnel for viewing and plantings. Once a year on August 1 at 9:52 am, the shadows cast by two of the spheres and their four adjacent poles align with shadow patterns outlined on the ground. The date commemorates the day in 1860 when William Ross bought the land that is today Rosslyn, VA.