Chiswick House
Completed in 1729 by the third earl of Burlington (also known for Burlington House—home of the Royal Academy—and Burlington Arcade on Piccadilly), this extraordinary Palladian mansion was envisaged as a kind of temple to the arts. Burlington was fascinated by the architecture he saw in Italy while on the Grand Tour as a young man and loosely modeled this building on the Villa Capra, "La Rotonda," near Vicenza and the Pantheon in Rome (note the colonnaded frontage and the domed roof, which is visible from the inside in the Upper Tribunal).
The sumptuous interiors were the work of William Kent (1685–1748), and it's easy to see how they made such a profound impact at the time; the astonishing Blue Velvet Room, with its gilded decoration and intricately painted ceiling, is an extraordinary achievement, as are the gilded domed apses that punctuate the Gallery (an homage to the Temple of Venus and Roma from the Forum Romanum in Rome). Such ideas were so radical in England at the time that wealthy patrons clamored to have Kent design everything from gardens to party frocks.
The rambling grounds are one of the hidden gems of West London. Italianate in style (of course), they are filled with classical temples, statues, and obelisks. Also on the grounds are a café and a children's play area.