In archaeology

Archaeology

Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...

, the term ring ditch refers to a regularly shaped circular or pennanular ditch cut. The term is most often used as a generic description in cases where there is no clear evidence for the function of the site: for instance where it has been ploughed flat and is known only as a cropmark

Cropmark

Cropmarks or Crop marks are a means through which sub-surface archaeological, natural and recent features may be visible from the air or a vantage point on higher ground or a temporary platform...

or a geophysical anomaly. The two commonest monument types represented by ring ditches are roundhouses (where the 'ditch' is actually a foundation slot or eaves drip gully) and round barrows. The term is not normally used for larger features than these, which would instead be described as 'circular enclosures'