The causeway, running roughly east to west for about thirty metres, sits just wide enough for a cart, with a stream that skirts its northern edge before turning south and passing beneath the road near its eastern end. A hydraulic ram now sits on top of the surviving section, a quietly incongruous piece of farm machinery planted on what was once a formal, tree-lined entry to a castle site.

Ordnance Survey maps from 1842 and 1905 both show the full roadway, running approximately ninety metres east to west toward the castle. By the time the 1937 survey was made, the eastern half had already disappeared. The older fabric of the approach is the more interesting part. Writing between 1905 and 1925, the local historian Grove White noted that under the causeway there had been, until quite recently, a very ancient arched bridge spanning the stream. By 1934, James Bowman was reporting that the stone bridge had already been replaced by a wooden one roughly fifty years earlier, and that it had crossed an old road about twenty feet wide. That earlier road, presumably predating the tidier nineteenth-century tree-lined section at the western end, suggests the approach to Ballyheen Castle had a much longer history than the Victorian landscaping implies. The causeway, the kind of raised, engineered embankment built to keep a road passable across wet or flood-prone ground, was a meaningful piece of infrastructure for its time, and its partial survival alongside a working stream gives some sense of how the castle site was originally organised within the landscape.