From the eighteenth Century onwards, as part of an interest in Romanticism, it became fashionable to construct features on ones land that served little utilitarian purpose.

Although by no means all structures took the form of mocked up ruins, it formed a significant class of 'folly'.

As far as I am aware, nobody built follies in the form of ruined contemporary buildings. Instead follies almost invariably masqueraded as the ruins of temples and other buildings from Classical Antiquity. A relatively late example of this is Maybeck's Palace of Fine Arts, built for the San Francisco's International Exposition of 1915.

Follies: Pictures