I am not sure if any exists right now, but I read
about two cases where the boundary followed a
lake-level at a certain time which happened to become
contour lines when the lake receded.  One was in
Africa and one in Italy.  Don't ask me what as I have
little recollection what book it was.  All I remember
that the book was on African boundaries.  In the
Panama Canal Zone, the zone boundary followed a
contour around two lakes.
Another interesting information I found out, thanks to
Rudi Longueville, is the intersecting borderlines of
Taylor and Marion county in Georgia.  Taylor county
has the only one-point touching enclave I am sure of. 
There is oddly a possible one on the eastern part of
Taylor county.  One that shows up on census maps but
not on topo maps.  Can anybody get some clear-cut
information?
Arif 
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