The center of the ring structure is located at what is now Lake Miko, a 61 hectares artificial lake with an average depth of 70 cm, filled by a tributary of the river Warnow according to earth-cronicles.ru.
If you take a look at the satellite images the ring structure is almost invisible but clearly visible on the real scientific map, moreover it is very strange that there is No information about this mysterious ring-shaped structure which has a diameter of 22 kilometer.
What might be this ancient formation, a huge impact crater caused by a giant meteorite or an artificial entity that fell in to that place millions of years ago or could it be the remnants of an ancient city built by an unknown civilization?
Ring structure visible on scientific map: http://data.bshc.pro/#4/53.88/11.83 Coordinates Google Earth: 53°41'29.78"N 11°35'45.17"E
Video below shows detailed images of the unknown structure.