Whilst the Down Survey of 1655-6 marks a castle in this general area, and the site retained the name ‘Castle’ on maps as late as 1939, what remains today appears to be a 19th-century folly rather than a genuine medieval fortification. The structure serves as an arched gateway leading to a courtyard, its design incorporating romantic Gothic Revival elements that were fashionable amongst the landed gentry of the period.

The gateway itself is a substantial construction, with an entrance passage measuring 4.2 metres long and 3.1 metres wide, built from thin, roughly coursed flagstones and topped with a flat-arched vault. The thick walls, at 1.3 metres, support this vaulted ceiling whilst a small rectangular tower projects from the northern side. This tower, measuring just 2.3 by 2.1 metres externally, contains a spiral staircase accessed through a narrow, round-arched doorway. The stairs, lit by arrow loops, lead to a compact first-floor chamber that measures 3.3 by 2.2 metres, with a square-headed window overlooking the approach. Above this level, the walls step outward to create a walkway complete with gutter-holes, mimicking the defensive features of authentic medieval towers.

The site holds deeper historical significance beyond its current incarnation. Records from the Journal of the County Kildare Archaeological Society note that Lyons once contained a hamlet of the same name, which met a violent end in 1612 when government troops burned it to the ground. The location is also marked by the ruins of an old parish church, suggesting this was once a thriving settlement before its destruction. Whether the current ‘castle’ gateway incorporates any genuine medieval masonry or stands entirely as a Victorian romantic fantasy remains uncertain, but it serves as an intriguing architectural footnote to a site with genuine historical tragedy in its past.