If you like miniature Greek temples then this is the folly for you. From a distance it looks like a bandstand, but as you get closer you realise that it would be crowded with more than one musician there. This is the secret of what a 'folly' is - a building designed to enhance the view of the landscape without really being of any practical use.
The Beacon was built in 1830 on a design by Vulliamy, making use of materials which were left after Purbrook House was demolished. Eight doric style columns support a domed roof, with a flagpole sticking out of the top. The story was that George Staunton, like the monarch, had the flag flying when he was in residence (in the house, not in the Beacon, obviously).