The plain moraine plateau has only a few natural and artificial ponds and also groups of clay pits. The pattern of the Vistula terraces is asymmetrical. The left side consists mainly of two levels: the highest one contains former flooded terraces and the lowest one the flood plain terrace. The contemporary flooded terrace still has visible valleys and ground depressions with water systems coming from the old Vistula – riverbed. They consist of still quite natural streams and lakes as well as the pattern of drainage ditches. The right side of Warsaw has a different pattern of geomorphological forms. There are several levels of the Vistula plain terraces (flooded as well as formerly flooded), and only a small part is a not so visible moraine escarpment. Aeolian sand with a number of dunes parted by peat swamps or small ponds cover the highest terrace. These are mainly forested areas (pine forest).