A rondel or roundel enclosure is a type of circular prehistoric earthworks enclosure found in Europe. Since being discovered in the 19th century, three types have been distinguished. One type consists of two semicircular ditches forming a circle and separated by causeways at opposing entrances. Another type consists of multiple circuits of ditches interrupted with entrances at cardinal or perhaps astronomically-oriented points and also having an internal single or double timber palisade. A third type consists of a single ring ditch.
They normally have a diameter of around 80m although much larger examples are known. Aerial archaeology has recorded many possible rondel enclosures across Central Europe, especially in Bohemia, Slovakia, Austria, and recently in Hungary, but few have been excavated. A pair of roundels are known at Bylany and all seem to be associated with settlement sites. Dating from pottery found in the ditches connected with the Stroke-ornamented ware culture of the Neolithic period although some may be slightly later.