Found in Germany, Austria, Czech Republic, Slovakia, as well as the adjacent parts of Hungary and Poland. A stretch in the center of Europe some 800 km, or (500 mi) has numerous circular enclosures. Mostly across the Elbe and Danube basins. In German, they are called Kreisgrabenanlagen, “rondels” and “rondeloid”.
Most of the circles are actually elliptic. The best known and oldest of these Circular Enclosures is the Goseck circle, constructed c. 4900 BC. It is only a few that are approximately circular. One other example at Meisternthal, is an exact ellipse with identifiable focal points.
Preceding to comparable circular earthwork or timber enclosures in Great Britain and Ireland. Around 3000 to 1000 BC (late Neolithic to Bronze Age). It contrasts the long lifeline of “Megalithic” cultures. Neolithic roundels were surprisingly narrow, lasting only about 200–300 years (from roughly the 49th to 47th centuries BC).
It’s believed cultures associated with the circles were: late linear pottery culture; stroke-ornamented ware (or, middle danubian); and, lengyel (or, moravian painted ware).

Krpy
In 1886, the earliest roundel to be described was in Bohemia, by Woldrich (Kropáčova Vrutice). It was only with aerial surveys in the 1980s and the 1990s that ubiquity of the entire region became apparent. From the area three types of circular enclosures have been distinguished:
1) Two semicircular ditches forming a circle, and separated by causeways at opposing entrances;
2) Multiple circuits of ditches interrupted with entrances at cardinal or astronomically-oriented points. Also, having an internal single or double timber palisade; and,
3) A single ring ditch.

Time, and groups working together
Interpreted as survival, these structures probably had cultic purpose. Most of them are aligned, and seem to have served the function of a calendar. This the case with the “gates” or openings of many of the roundels. Including of Quenstedt, Goseck and Quedlinburg. It helped them with agriculture, farming and calanders.

Known Neolithic Circular Enclosures
Slovakia
From aerial surveys, about 50 neolithic circle candidates exist (Ivan Kuzma 2004). There are 15 known (Lengyel). Largest of these are (with outer diameters of more than 100 m): Svodín 2 (140 m), Demandice (120 m), Bajtava (175 m), Horné Otrokovce (150 m), Podhorany-Mechenice (120 m), Cífer (127 m), Golianovo (210 m), Žitavce (145 m), Hosťovce (250–300 m), and Prašník (175 m). Others include: Borovce, Bučany, Golianovo, Kľačany, Milanovce, Nitrianský Hrádok, Ružindol-Borová.

Hungary
Aszód, Polgár-Csőszhalom, Sé, Vokány, Szemely-Hegyes.

Czech Republic
15 known sites, all dated to the late Stroked pottery (Jaroslav Ridky 2004): Běhařovice, Borkovany, Bulhary, Krpy, Křepice, Mašovice, Němčičky, Rašovice, Těšetice, and Vedrovice.

Austria
47 known sites with diameters between 40 and 180 m (Doneus et al. 2004): Lower Austria: Asparn an der Zaya, Altruppersdorf, Altruppersdorf, Au am Leithagebirge, Friebritz (2 sites), Gauderndorf, Glaubendorf (2 sites), Gnadendorf, Göllersdorf, Herzogbirbaum, Hornsburg, Immendorf, Kamegg, Karnabrunn, Kleedorf, Kleinrötz, Michelstetten, Moosbierbaum, Mühlbach am, Manhartsberg, Oberthern, Perchtoldsdorf, Plank am Kamp, Porrau, Pottenbrunn, Pranhartsberg, Puch, Rosenburg, Schletz,
Simonsfeld, Statzendorf, Steinabrunn, Stiefern, Straß im Straßertale, Strögen, Velm, Wetzleinsdorf, Wilhelmsdorf, Winden, Würnitz.
Upper Austria: Ölkam.

Poland
Biskupin (Greater Poland)
Bodzów, Rąpice;
Pietrowice Wielkie (Upper Silesia);
Nowe Objezierze (Pomerania);
Near Łysomice (Kuyavian-Pomeranian);
Near Tylice (Kuyavian-Pomeranian);
Drzemlikowice (Lower Silesia); and,
Vinoř roundel near Prague.

Germany
Saxony Anhalt, outer diameters between 72 and 110m (Ralf Schwarz 2004): Quenstedt, Goseck, Kötschlitz, Quedlinburg, and Heldenberg;
Saxony: Dresden-Nickern (3 sites), Eythra (2 sites), Neukyhna (3 sites);
Bavaria: Lower Bavaria: Eching-Viecht, Künzing-Unternberg, Meisternthal, Moosburg an der Isar-Kirchamper, Oberpöring-Gneiding, Osterhofen-Schmiedorf (2 sites), Stephansposching Wallerfing-Ramsdorf, Zeholfing-Kothingeichendorf;
Upper Bavaria: Penzberg;
Nordrhein-Westfalen: Borchum-Harpen, Warburg-Daseburg;
Niedersachsen: Müsleringen;
Franconia: Hopferstadt, Ippesheim; and
Brandenburg: Bochow, Quappendorf.

Bibliography: Neolithic Circular Enclosures in Europe, International Workshop in Goseck (Saxony-Anhalt, Germany) 7.-9. Mai 2004 (abstracts).

Gillian Varndell, Peter Topping (eds.), Enclosures in Neolithic Europe, Oxbow, 2002, ISBN 9781842170687.

Peter F. Biel, “Measuring time in the European Neolithic? The function and meaning of Central European circular enclosures” in: Iain Morley, Colin Renfrew (eds.), The Archaeology of Measurement: Comprehending Heaven, Earth and Time in Ancient Societies, Cambridge University Press, 2010, ISBN 9780521119900, 229-243.