Montleek: Robert, is it possible that in Western Europe, the regional lects have been preserved better, while in eastern Europe are preserved worse? There was communism/socialism in Eastern Europe, therefore more tendency not to continue speaking with regional lect.
Germany is a very chaotic situation with a dialect in every town or village.
Dutch is actually spoken up near the Dutch border, but the form is not intelligible at all with Dutch across the border. You get into the different dialect in every town here.
Danish spoken a bit up by the Danish border.
Sorbian is spoken in the central east.
Frisian is spoken in the northwest and in the far north.
There are up to 138 separate languages within German by my calculation and splitting down to dialects, there must be many more, surely hundreds and maybe over a thousand. There are 3-4 languages within the Macro-Dutch spoken on the border and a dialect in every town. The Danish spoken in the north is not very dialectally diverse. Frisian is spoken as North Frisian and Saterland Frisian, but there may be up to five languages inside North Frisian. Sorbian is spoken in two forms, Upper Sorbian and Lower Sorbian, and both are separate languages.