What I did today was go to aww Strawberry Hill House in Twickenham (Greater London). It looks like a castle, but is actually a house that - in stages in the 18th century - Horace Walpole turned into a Gothic creation. Wikipedia describes it:
Walpole rebuilt the existing house in stages starting in 1749, 1760, 1772 and 1776. These added gothic features such as towers and battlements outside and elaborate decoration inside to create "gloomth" to suit Walpole's collection of antiquarian objects, contrasting with the more cheerful or "riant" garden. The interior included a Robert Adam fireplace; parts of the exterior were designed by James Essex. The garden contained a large seat shaped like a Rococo sea shell; it has been recreated in the 2012 restoration.