defined, specific space. Property lines separating lots in a subdivision, and the fen-
ces that may correspond to such a line, represent short, legally defined borders
drawn by certified surveyors, whose methods, standards, and techniques are
accepted by courts of law in many countries. Borders at this scale, which usually
are only a few hundred feet in length, can be defined with considerable precision.
Borders at a larger scale, such as international boundaries, frequently exhibit much
less precision, and are many times disputed by one or both countries separated by
the border. On the other hand, in a few locations borders between sovereign states
remain undefined and unmarked, even in the 21st century. Borders not only define
zones of control, they also affect the rate of many geographic processes, such as
migrationandcultural diffusion, because they tend to delay or completely pre-
vent movement across space.
The practice of clearly identifying thelocation of international borders has
become commonplace only in the last two to three centuries in many parts of the
world. Previously, borders were frequently defined by less distinct boundaries
known as marchlands or frontiers, which provided only a general idea of where
the rule of a sovereign or state came intoeffect. Of course, some borders were
marked in ancient time by defensive walls that were virtually impenetrable and
reached lengths of many miles. The Great Wall of China and Hadrian’s Wall in
Great Britain are two of the most famous examples. These are also examples of
what political geographers termrelictboundaries, meaning that while they still
appear on thelandscape, they no longer function as a boundary. There are more
modern relict boundaries as well, including the Berlin Wall and the famous “Iron
Curtain” lying between Eastern and Western Europe during the Cold War. The lat-
ter was an imaginary boundary, in that there was no real curtain, although the bor-
der certainly was sealed and operated as a real barrier, keeping millions of people
inside. Relict boundaries serve to remind us that the location of boundaries is
never permanent, and political borders in particular tend to change or lose their
relevance over time.
In addition to relict boundaries, geographers identify political boundaries based
on various criteria. A common type of international border is thenaturalboundary,
which is represented by a naturally occurring physical feature. The Danube River
in Eastern Europe, for example, serves as the international border between several
countries as it flows from Germany toward the Black Sea. The Himalaya range in
southern Asia is another natural feature that serves as a political boundary. The
termphysiographicboundary is also applied to this type of boundary. On the other
hand,geometricpolitical boundaries are drawn artificially without consideration
of the natural terrain. A geometric border must be surveyed, and in many cases
is indicated by a fence, wall, or some other constructed marker. These types of
divisions often correspond to line of latitude or longitude, and are usually created38 Boundaries