I am curious about Christiania, I have heard about that. I am curious how taxes work there. For instance if you earn money there inside that zone, do you have to declare that income? What is the level of "anarchy" exactly in that zone?

That are really good questions to which I do not have answers to be honest. With some further internet research, the answer may be revealed :) They apparently bought the place some years ago from the local government.

Regarding taxes, I even don't know how it is at ADM here just outside Amsterdam. I go there a couple of times a year when they have their music and art festivals. Super nice! Next time I'll ask the people who live there.

In the mid 90s I was at a similar place in Maribor (Slovenia), Pekarna, also a free haven, quite small, but again a place where people lived forming their own community, and where the police would never step a foot insight, so anything goes, whatever you felt like. http://www.pekarna.net/node/17

You know of the existence of the mini states? Micronations they are called. These are self proclaimed countries with their own flag, currency and all. They do all the things that are required to be a country. The only thing they generally don't have, is the recognition being a country by all the other countries in the world. There are micronations on oil rigs, on small islands, and so on. https://en.wikipedia.org/wiki/List_of_micronations