High Quality Content by WIKIPEDIA articles! In architecture, a folly is a building constructed primarily for decoration, but either suggesting by its appearance some other purpose, or merely so extravagant that it transcends the normal range of garden ornaments or other class of building to which it belongs. In the original use of the word, these buildings had no other use, but from the 19th to 20th centuries the term was also applied to highly decorative buildings which had secondary practical functions such as housing, sheltering or business use.