Dundrum Castle, Dundrum, Co. Dublin

What visitors see today is primarily a late 16th to 17th-century tower house, but excavations between 1988 and 1991 revealed something far older lurking beneath; the remains of a medieval castle dating back to the 12th century. The original fortress was built around 1187 by Sir John de Clahull, a Norman knight who clearly understood the strategic value of this elevated position overlooking the river valley.

The archaeological work uncovered some remarkable features from the early castle, including a substantial defensive ditch, or fosse, measuring seven metres wide and 1.4 metres deep that encircled the hilltop. This wasn't just a simple ditch either; it was equipped with a sophisticated triple-slotted drawbridge system that connected to a gatehouse, creating a formidable entrance complex. The excavations yielded everyday objects that bring the medieval period to life, including Leinster cooking ware pottery, a buckle, and a socketed arrowhead, all testament to the daily life and occasional conflicts that played out here.

Perhaps most intriguing are the castle's practical features that speak to medieval engineering ingenuity. A stone-lined watercourse was discovered running beneath the base of the wall, likely part of the castle's water management system. The builders also incorporated a garderobe shaft within the wall thickness; essentially a medieval toilet that would have channelled waste away from the living quarters. These details, combined with the surviving two-metre-wide outer wall sections, paint a picture of a well-planned fortress that balanced defensive needs with the practicalities of daily castle life. Today's tower house, built centuries later, stands as a testament to the site's enduring importance through different eras of Irish history.