Excavation at a crop-mark site found close to Annan, Dumfries and Galloway, revealed evidence of a ring-ditch containing a number of intriguing internal structures. Initially this was presumed to be a prehistoric monument, but pottery and radiocarbon dating, unexpectedly, indicated that the main structural phase of the site falls between the 11th-13th centuries AD. This suggests that a degree of caution is required when interpreting crop-mark sites on morphological characteristics alone. Moreover this excavation makes clear that morphological interpretation can have a constraining influence on excavation strategy, so caution is required when designing fieldwork programmes.