Funded by the vast profits from the slate mine of the Caribbean sugar-plantation owner and anti-abolitionist Baron Penrhyn, and extended and embellished by his great-great-nephew, this immense 19th-century neo-Norman folly is both tasteless and formidable. Flanked by a Victorian walled garden, the creeper-clad stone walls of the Norman 'fortress' embower the neo-Gothic hall with its darkly extravagant rooms, complete with intricately carved ceilings, stained-glass windows, opulent furniture and even early flushing toilets. There's also an on-site industrial railway museum.

Llandygai village, which begins immediately outside the estate walls, was developed as a model settlement for workers in Penrhyn's slate quarry. The castle is 1.5 miles east of Bangor, and buses to Llandudno stop at the gate.