The one on the demesne of Leamcon House in west Cork does something more peculiar: it contains the stream inside itself. Built into the body of the bridge is a lintelled rectangular chamber, roughly 1.8 metres high, four metres long east to west, and less than a metre wide north to south. Water enters from the north through a small lintelled opening, passes through this enclosed internal space, and exits southward through a taller opening partially divided by a thin, sloping slab. Above the inlet, a horizontal row of three additional lintelled openings all connect into the same central chamber. An overflow channel runs westward through the bridge, and the upstream approach was cut directly from the bedrock.

The arrangement is genuinely unusual. A lintelled ope, to use the technical term, is simply an opening spanned by a flat horizontal stone rather than an arch, and the concentration of them here, each precisely sized and oriented, suggests that whoever designed this bridge was doing something more considered than simply getting water from one side to the other. The chamber's dimensions are tight enough to feel purposeful, possibly related to controlling flow, managing sediment, or channelling water for use on the estate. Leamcon House sits in the Mizen Peninsula area of County Cork, a part of Ireland where the landscape itself is often shaped by careful, generations-long management of land and water. The rock-cut upstream channel reinforces the impression that the whole system was engineered with some deliberation, though exactly when and for what precise purpose remains unrecorded.