I've seen discussions here previously about the "verticality" of
borders, and have attached an interesting map I received from the office
of the Berlin Senate that dealt with the exchange of territories between
the DDR/East Germany and Allied occupied Berlin.

As you can see, the access road which was given to the Allies is SE of
railway tracks that passed through Steinstuecken, and that there is a
road across the tracks at the north end of the exclave. It appears that
a train travelling south from West Berlin passed through a mile of East
Germany, and as it went under the bridge that carries this road, it
passed through the west for perhaps 20 feet, assuming the border
extended downward at least to the railway tracks. Then the train, after
passing under the bridge, was once again in East German territory (which
for the width of the tracks and perhaps 50 meters was within
Steinstuecken). After passing into Steinstucken-West territory, it
would travel another 100 meters or so, and enter East Germany again.

Is it my imagination, but does it appear that in exchange for ending
Steinstuecken's isolation as an exclave, that an exclave of East Germany
was created inside West Berlin? Or, can a bridge be part of one country
and the ground under it be in another?

Contrast the situation in Steinstueken with that shown in the attached
extract of a map of the Belgian-German Vennbahn borders. Is someone in
Germany who passes under the bridge that carries the Belgian railroad,
actually in Belgium while he or she is under the tracks? Notice the
Ruitzof "exclave" markers at B and C - is this really an exclave of
Germany, or are there breaks in the border that mean the tracks are in
Germany for short stretches? Note also border point 656A (lower right
of the map).

Regards

Len Nadybal