Johann Heinrich Müntz's painting of Strawberry Hill shows Horace Walpole's Gothic castle in its heyday. Walpole collaborated with architect Robert Adam to create a revival in Gothic architecture. Its library was the first Gothic Revival library in the world. By 2004 Strawberry Hill had fallen into such extreme disrepair that it was listed by World Monuments Fund as one of the world's 100 most endangered heritage sites. Its two-year restoration cost £9 million, money well spent to bring this gem back to its former glory. (Click the title link to see a Telegraph slide show.) The house is due to be reopened to the public on 2 October. The bad news is the cost of admission: £8 or £7. Pre-booking is essential: call 020 8744 3124.