He was in a garden of fantasies where no natural barriers held.

Unsettling because such things have no natural barriers, nothing that can contain their spread.

The elf turned and fled then, back through the natural barrier.

Hills form a natural barrier on its northern and western sides.

The Oste river forms a natural barrier to the west.

In addition there are natural barriers that protect the area from Atlantic storms.

The area had high clusters of rock on three sides that would provide a natural barrier against the wind.

Keep the planet and its moon in front of us as a natural barrier.

The fat-moss had not been stopped by any natural barriers.

They'd crossed the Hoocheecoochee, the last great natural barrier before the city.