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, 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.