The house commanded a view of the valley and the works, which ‘at night, offer a truly magnificent scene, resembling the fabled Pandemonium, but on which the eye may gaze with pleasure’.

The castle stands in 158-acre (64 ha) of parkland, now called Cyfarthfa Park and maintained by Merthyr Tydfil County Borough Council.

The castle was designed in 1824 by the architect Robert Lugar for William Crawshay II, and built at a cost of approximately £30,000 using locally quarried stone.

Much of the decoration has a mock-Tudor feel; the small shields around the frieze, the tall pillars round the windows, huge Gothic doors and the superb red and clear glass windows that fill the rear of the hall, all add to the imposing grandeur.

The castle would have likely seen huge renovations in order to see the construction of the Y Siambr chamber and relevant government offices, including that of the First Minister of Wales.

[4] It has acres of walks and a miniature steam railway run by Merthyr Tydfil Model Engineering Society since 1987.

It has function rooms and a seasonal café,[6] a children's playground complete with a ‘Splash Pad’,[7] a 9-hole golf course,[8] bowling grounds and tennis courts,[9] and a fishing lake.

On 30 June 2007, Donny Osmond, who traces his family history to Merthyr Tydfil, performed the 'Donny Comes Home' concert in the park grounds.