As Scriptor has said, "old" is an adjective that has to be explained
and better defined. There could be several definitions of old:
- longest surviving with the same system of government
- longest surviving as one political unit
- with the oldest average population (though this is not a historical
definition, so I guess you didn't mean that)
- longest surviving civilisation
I actually hope that some debate on my answer will therefore develop
in the comments section, because although I try to give the best
possible answer, it is quite possible that others will come with other
candidates and alternative explanations.
So, there are several candidates to the throne.
As it happens, national ideologies add some reconstructed history to
the issue. A famous political scientists/sociologist by the name of
Benedict Anderson wrote in 1991 a book whose title describes this
phenomenon better than anyone else: "Imagined Communities". People
forge themselves a history and a national myth, relating themselves to
historical communities, but they are not necessarily really continuous
For example, Bulgaria, according to some sources, claims to be founded
in the 7th century and therefore a very old country indeed. However,
the modern country of Bulgaria just refers to this Bulgaria of
antiquities, but was since conquered and occupied by the Ottoman
Empire, by the Germans and the Soviets. Not only that, but the borders
have also changed since.
The relatively new Republic of Macedonia (or FYROM, which means
"Former Yugoslav Republic of Macedonia", and was the provisional name
of the country, as horrible as it sounds) has the same problem. While
its national founding myth relates to Alexander of Macedon (and
therefore to the Greek Antiquity era), there is no continuous line
between ancient Macedon and modern (FY)ROM, which was founded in 1991
- it was part of the Roman Empire, the aforementioned Bulgarian
Kingdom, the Ottoman Empire and Yugoslavia. In fact, it took up the
name FYROM (instead of Macedonia) in order to avoid a dispute with
Greece, also claiming to be descendant of that mythical Macedon.
So don't tell that to the Macedonian or the Bulgarians, but theirs are
not the "oldest" countries in Europe. The "oldest" countries
maintaining the same borders and government are much-much smaller.
We're talking about two contenders.
The second runner-up might be Andorra, a tiny principality in the
border between Spain and France. It has been founded in 880 and its
borders haven't changed since 1288.
But the winner is... San Marino, an even tinier republic located as an
independent enclave inside Italy. It claims to exist in the same form
and borders since the early 4th century, and there is certainly
documentation to support the idea that since the 1290s it has even
exactly the same form of government (though it claims also to be the
oldest republic, since its foundation).
By the way, there are only two other European states that are smaller
than San Marino. One is Monaco and the other is the Holy See (the
smallest country in the world). Monaco, too, had had the same regime
(that of the Garimaldi family) since the 1290s, but, alas, they had a
short period of French occupation in the 18th century and besides,
their foundation was slightly after that of Andorra.
The Icelanders among Google Answers fans might be crossed now, for not
having been mentioned. Their country is certainly part of the
oldies-club (though it hasn't been always independent) - their
relatively young island has been inhabited by the Norse in the 9th
century, and there might have been some settlement even beforehand.
<http://en.wikipedia.org/wiki/History_of_Iceland> . But then again,
other Island states have a much older history:
All of these nations are pretty small, especially the alleged winner,
San Marino. The only "large" country in Europe that can claim such a
relatively long history within the same borders is Portugal - it has
been founded 1128, and established its current borders in a process
that lasted until the late 15th century.
And this is without mentioning another old nation, the Armenians:
"Archaeologists refer to the Shulaveri-Shomu culture of the central
Transcaucasus region, including modern Armenia, as the earliest known
prehistoric culture in the area, carbon-dated to roughly 6000 - 4000
BC. However, a recently discovered tomb has been dated to 9000 BC."
(Wikipedia, <http://en.wikipedia.org/wiki/History_of_Armenia>). Don't
forget that according to the Armenian national myth, Noah had parked
his Arch in Armenia.
By the way, regarding geological history of what is Europe, the
Bulgarians claims - again - to have something really old: "You would
probably know or you will learn and appreciate with your own eyes once
you come here - WHAT THE RHODOPE MOUNTAIN IS:
* one of the oldest geological formations in Europe;"
I hope this answers your question. Please contact me if you need any
clarification on this answer before you rate it.