Forms part of a group of buildings attached to the North side of Craig-y-Nos, a country house over looking the River Tawe. The original house was built in 1842 and the North block and other additions, including the 150 seat theatre and auditorium, were built in 1891 by Bucknall and Jennings of Swansea for Adelina Patti, the renowned soprano who bought Craig-y-Nos in 1886.

The Theatre extension with a raised fly-tower, has red snecked facings, yellow brick dressings, and slate roofs. There is a pilastered facade to the entrance courtyard, forward from the clock tower, a triglyph frieze with a stucco panel under a pediment. The pediment has cherubs, swags, and a musical trophy, plus a full-size figure with a tambourine. The central pedimented doorpiece is masked by a later canopy and an Ashlar clock tower overlaps the corner of the theatre.

Internally, the theatre is linked by a corridor to the corner of the billiard room and the rest of the house. The interior is regarded as the most ambitious of the few private theatres in Britain and may be a miniature copy of the Bayreuth Opera House. It was probably designed by Jackson and Sons, decorators, of London. The auditorium (now lacking the South gallery) has four Corinthian columned bays, a curved exedra to the South and a curved apron stage, forward from the elaborate procenium arch, flanked by twin Corinthian columns and a swagged entablature with an open pediment to the AP cartouch topped by reclining figures and cresting. It has volute brackets to the coved ceiling with grotesque plaster work, and painted and plaster work arabesques to columns, walls and friezes with composer tablets, ornamental heating grills, and a balustrade apron with the orchestra pit underneath. The auditorium floor has levelling machinery for use as ballroom. The stage has some original hangings and scenery, including a curtain drop of Adelina Patti as Semiramide, designed by Hawes Craven, a leading Victorian theatrical painter. The Theatre is listed as Grade I, because of the interiors.
(Source 'Addition to CADW List of buildings of special architectural or historical interest, list No. 28, district of Brecknock')
Ian Archer, RCAHMW, 28th January 2005