A folly is by definition an ornamental structure (although some do have a purpose). They are to be viewed as part of the scenery and were usually based on the picturesque ruins of the classical World. They are often eccentric in design or construction and there is often an element of fantasy or make believe in their construction. Some Irish follies were built as famine relief projects to provide employment.
One of the finest examples of a 'cottage ornee' in Europe Fantasy houses such as Swiss Cottage were popular with the gentry in the 19th century where they could play at being peasants [...]