Built on parkland beside the River Tawe in the upper Swansea Valley, it is located on the southeastern edge of the Black Mountain.

The family cleared a large plantation of 80-year-old fir trees which stood between the castle and the quarries above, which were said to be home to a local population of red squirrels.

[1] Having achieved great success as a singer, Patti spent the rest of her life at Craig-y-nos, leaving it only to sing in the premier opera houses of Europe and to tour the United States.

[2] After her second marriage, to French tenor Ernesto Nicolini, she embarked on a major building programme at the castle, adding the North and South wings, the clock tower, conservatory, winter garden and theatre.

[3] After making her last public appearance in October 1914, when she sang for the Red Cross and filled the Albert Hall, she spent the rest of her life at Craig-y-nos with her third husband.

[5] Built to be Patti's own private auditorium, it was designed by Swansea architects Bucknall and Jennings, with input from Sir Henry Irving.

[6] Ten Corinthian columns support the ceiling, and in between these are the names of composers such as Mozart, Verdi and Rossini, all gilded and surmounted by Madam Patti's monogram.

[6] The stage area was originally fronted by blue silk curtains, with a back drop that illustrates Madam Patti riding in a chariot, dressed as Semiramide from the opera of the same name by Rossini.

Journalists from international newspapers including The Daily Telegraph, Le Figaro and the Boston Herald were also invited as house guests to report on the opening.

[6] Final rehearsals occurred in the afternoon with the Swansea Opera Company, before a specially chartered train arrived at Penwyllt with the performance guests.

[3] At the start of the 20th century, Patti had one of the first motor cars in Wales, and is reported to have raced a local doctor from Swansea to Abercrave for a small wager.

[3] After Adelina Patti's death in 1919, the castle and the grounds were sold to the Welsh National Memorial Trust for £11,000 in March 1921, an organisation founded to combat tuberculosis in Wales.

[13] In a project supported by the Heritage Lottery Fund, the Sleeping Giant Foundation charity, the Wellcome Trust Centre and University College of London, in 2007 an exhibition at the Welfare Hall, Ystradgynlais, showed relics and recorded recollections of patients from its time as a TB sanatorium.

[12] The Welsh Office declared Craig-y-nos Castle and its unique theatre surplus to requirements soon after the opening of the new Community Hospital in nearby Ystradgynlais.