You should all come to Belgium! We have a different dialect in every town and village. Flanders (the Dutch-speaking part) is a bit over 13 000 km² and often it is almost impossible to understand each other when people speak their own dialect. I am from the east and I went to colleg in the west of Flanders, where I met mostly students from the West. Honestly, it took me a year to be able to fully understand a conversation . Even now, after 6 years of living here, I still occasionally have some problems.
Apart from dialects, there are also regional accents. Most people can usually tell by their speech where someone is originally from.
Nowadays, a mix is emerging. Not really standard Dutch, but not a dialect either. Standard Dutch is often considered high-brow so most people mix in some slang, dialect words and keep their regional accents.

These days though, dialects aren't spoken as often anymore. Standard Dutch is used on tv, in school, every official situation. So everyone of course understands standard Dutch but not everyone can speak it. Especially the older generation keeps speaking their dialect. Also, people move a lot more than they used to. My parents for example: my mom and dad are from different regions and speak different dialects but they moved to a third region (my dad as a kid, my mother after they married), but they don't speak that dialect. So my parents speak sort of a standard Dutch to each other and my brother and me. I never learned the dialect from my town although I can understand it.
In the West, dialects are more popular though. Which is one of the reason I had trouble understanding my friends for such a long time. They weren't used to talking standard Dutch (although they were able to) so I had to adapt. My best friend switches between dialect when she's with other friends and standard Dutch when she's just talking to me .