Land swaps can be a royal PITA; the highest point in Finland is most of the way up a mountainside; the peak is just across (as in, within a stone throw) the border, in Norway.
To mark the centennial of Finnish independence, there was a campaign in Norway to give the Finns a few hundred square metres of Norway, so that they could get a highest point which was indeed a local maximum.
Too bad the Norwegian constitution says you cannot give away bits of the country; a land swap was suggested to ensure both countries remained the same size afterwards, but apparently this, too, would violate the constitution...
A couple of Norwegian conscripts technically invaded Finland earlier this year; while patrolling the border, they accidentally strayed onto the other side.
(Not as hard as it may sound; the border isn’t marked as such, only with the occasional pole here and there.)
I guess it depends on whose definition you use; Norwegian papers at the time quoted experts (presumably a professor of international law, though I can’t remember) who claimed that legally speaking, having troops in uniform venturing into another country counted as an invasion.
Considering all the notes being passed back and forth afterwards, the conscripts must be kicking themselves for not keeping quiet about it; they weren’t observed by Finnish border guards; rather, they notified their officers when returning to base that they’d crossed the border; the army notified the DoD, which notified the Foreign Department, which notified the Finns, who said ‘Huh?’
The Dutch actually have a continuing conflict with Germany about a maritime area: the Dollard/Dollart. Not that it's an actual problem: all practical affairs have been arranged in harmony, but still both countries' claims overlap, and in fact the last few metres of the pier of Delfzijl are in Germany according to their interpretation...
