Circular enclosures from the neolithic age are found in central Europe

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).

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 probaby 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

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.

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.

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.

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.

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.

The neolithic flint mines at Spiennes Mons is one of the most culturally significant centres of world heritage

After a couple decades of believing there was something odd about the area. Finally, in 1867, a railway line was dug that cut through 25 mining shafts. It is the origin and, discovery of the site Spiennes Mons.

Covering more than 100 ha (250 acres), it is the largest and earliest concentration of ancient mines in Europe.

Brief synthesis
Covering essentially an agricultural area. The Neolithic Flint Mines of Spiennes occupy two chalk plateaus located south-east of the city of Mons. Though below, underground, the site is an immense network of galleries dug out by almost 10,000 year old neolithic populations.
The area houses the biggest and earliest concentration of ancient mines of north-west Europe. In operation for many centuries, the areas origins still remain moderately illustrative in the development and adaptation of modern mining techniques. In order to exploit large deposits of materials the site was used to dig down shafts of .8 to 1.2m in diameter to a depth of about 16m. Populations could pass thru blocks of flint about 2m length. They used a technique called ‘striking’. Where they would free the blocks from below with the support of a chalk wall, shoring up the block, removing of the wall, and the props and thus lowering of the block. Where they could then get it up and out the shaft, break down and analyze further for flintknapping.

Largest & longest neolithic flint mine
In the neolithic period, from the last 3rd of the 5th millenium, until the 1st half of the 3rd millenium (almost 2000 years). The site was used for extensive flint mining.

Tree falling tools, for huts, canoes and more
Production aimed at the manufacture of axes to fell trees; and, long blades to be used, and transformed into tools.

Where did they live while mining?
A camp was discovered at the site comprising two irregular concentric pits at a distance of 5 to 10m. The archaeological artifacts discovered are characteristic of the Michelsberg culture (neolithic culture in the center of Europe) discovered in the mining sector. It was a giant working mans camp site.

Metal ages
After the metal ages, the area turned to agricultural land. In the 1700s, armies of Louis XIV dug out a pit of 3m in depth accompanied by an earthen wall. By the 1800s they started manufacturing of gun flints again. Now if your in the Belgium or northern France area. Definitely worth checking out.