Tiny enclaves of one country inside another

[AndiFlatland]

If you have access to a map of large enough scale, have a look at the borders between Belgium and Holland, and between France and Spain.
In Holland, there is a town called Baarle-Nassau, very close to the border with Belgium. The town has a raggedy border around it, and there are several very tiny satellite enclaves, which I assume to be part of Belgium.
Just north of the Pyrenees, and east of Andorra, there are a few similar enclaves of varying small sizes, and I assume that these are part of Spain, although there don't seem to be any towns within them.
Does anybody know why these enclaves exist, and what historical incidents may have led to their creation?
Does anybody know of any other regions around the world like this?

[jno]

http://en.wikipedia.org/wiki/Baarle-Nassau

[dundurn]

Try this link Andi for some others http://members.aol.com/marismits/LoclGeo.htm

The most usual reason is that a later "high level" border(like a country boundary drawn down the ridge line of a mountain chain) conflicts with the fact that the only access route to the area is from the "other" country. The enclaves are usually small, of no significant commercial importance and both governments concerned are happy to let matters stay as they are. We have some minor examples within the UK where apparently solid county boundaries conceal the fact that there are little enclaves of another county contained within them.