These form hills or vales depending on their relative resistance to erosion.

Elaborate walls were constructed by connecting carefully cut stones forming terraced hills.

The interior floor, while generally level, has a number of low irregularities forming small hills.

These are eroded and form steep hills, valleys and bluffs.

There are numerous escarpments forming small prominent hills within this area.

Sorbet can be scooped, and will form soft little hills on a cone or in a cup.

The bones were piled everywhere, lying on the open ground or forming hills cemented together by the cold.

Beyond the high tide mark, if the beach is low-lying, the wind can form rolling hills of sand dunes.

Escarpments form small prominent hills within the plain.

The generals suggested to pile up earth to form small hills and replenish their equipment.