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 consist 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 Vistula old – 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 plain Vistula terraces (flooded as well as former flooded once) and only small part and 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).