What was once an L-shaped tower house, strategically positioned in the southwest corner of an ancient cashel, now exists only as foundation stones on a limestone crag. The castle's location on a southeast-facing slope would have provided both defensive advantages and pleasant living conditions for its medieval inhabitants.

Thomas Johnson Westropp, the prolific Irish antiquarian, documented the site in the early 1900s when somewhat more of the structure remained visible. He noted seeing fragments of an old house with a tall chimney still standing; a tantalising glimpse of what must have been an impressive fortified residence. Unfortunately, the castle met a rather pragmatic fate during the 18th century when much of its stone was quarried and repurposed for the construction of nearby Altavilla House, a common practice that saw many of Ireland's medieval structures transformed into the building blocks of Georgian estates.

Today, visitors to Milltown North will find little more than ground-level traces of this once-proud tower house, though its historical significance hasn't been forgotten. The site has been under preservation order since 1977, ensuring that what remains of this medieval stronghold is protected for future generations. The surrounding cashel, an earlier fortification that would have enclosed a settlement, provides context for understanding how this corner of Limerick was inhabited and defended across the centuries.