There is a natural arch of marble still in one part of it.

Half-hollow now, the trunk had split and splayed outward to form a natural arch.

The natural arch that admits one to Mammoth Cave has a span of seventy feet.

Before them the upper branches of the nearest trees formed a natural arch above the picture.

It is a remarkable natural arch, through a rocky wall or rampart, one hundred and fifty feet thick.

Its projecting point terminates in a high rock, through which is a large hole, forming a natural arch.

Once we passed under a natural arch of ice, built in evident disregard of all principles of architectural stability.

My guess is they once formed the ceiling, eventually fell away, and the ice remained in a natural arch.

Nestled in the peaks of the Guizhou province, the immense natural arch and featured walls of Chuanschang were awaiting a visit.

These lintels had all fallen, and the stones above formed broken natural arches.

There can be no other explanation for the plethora of overtly un- natural arches out there.

Tourists take in the Double Arch, a famous pair of natural arches, at Arches National Park, Utah, September 2009.

"The best crabs are between Scutari and the natural arch."