Asia's oldest Gothic theatre (1887), still hosts plays and events. Interesting for architecture/theatre buffs, skippable if you're short on time and have already seen The Ridge/Christ Church next door.
The Gaiety Theatre opened on 30 May 1887, during Queen Victoria's Golden Jubilee year, designed by architect Henry Irwin in Victorian Gothic Revival style as part of a larger Town Hall complex housing a ballroom, armoury, police office and bar. Structural instability forced a partial demolition and rebuild in the early 20th century, and the complex hosted amateur theatricals attended by Viceroys and colonial officials, including a young Rudyard Kipling as a performer. A major restoration completed around 2009, costing over Rs 11.5 crore, revived it as Shimla's hub for performing arts.