Ash pit, an archaeological term, is one of the remains left by ancient humans. Compared with architectural relics and tombs, it contains more materials, including many items left by people who lived here at that time intentionally or unintentionally, such as pottery. Its characteristics are mainly gray or mixed with other colors formed by decomposition of organic matter, such as brown. The soil is softer than other soils in the same area and is mainly formed by abandoned wells and caves.