Man-made underground passage in Shanrath East

Shanrath East in County Kildare holds a curvilinear shadow inside a levelled rath, visible only when overhead light catches the S sector. Whether people dug a passage there or simply cut a ditch remains unknown, but the shape resists ordinary explanation. A rath is a threshold place, and thresholds often hide rooms. The field has forgotten the entrance while preserving the line of the way.