The centre is unique in its use of covered natural rock.

A staircase cut from the natural gray rock curved down to the level below.

That's a natural rock you find a lot of around here.

From what she'd been told, the granary was also stored in natural rock.

"Doesn't the floor need to be natural rock or earth?"

In Carlos's time, the road had been little more than a rough track of natural rock.

Now and then, light shot out from the natural rock for a distance of perhaps 5 or 6 feet.

However, sometimes natural rock may be used to create a lower platform.

The floor as well would be of natural rock.

She has been making her mark on natural rock as well.