J´ai failli oublier wikipedia:
http://fr.wikipedia.org/wiki/Odessa
C´est apparement une grande ville, jumelée avec Marseille.
J´ai aussi trouvé quelques trucs intéréssants sur le sujet dans wikipedia Anglophone (Article sur hl2):
"The environments in Half-Life 2 are varied, ranging from the Eastern European-styled City 17 and surrounding areas, to the massive Combine Citadel. There is a general Eastern European "feel" present throughout the human-populated areas, and several hints indicate that City 17 is based on Sofia, Bulgaria, the hometown of the art director of Half-Life 2, Viktor Antonov. Antonov wrote that Eastern Europe was favored as a setting for the game as it is capable of depicting a combination of both new and old architecture, creating a city with history; "gothic themes associated with Prague and vampires" were also overlooked in favor of a different aspect of the region[8].
City 17 has both a general resemblance to Sofia as well as frequent appearance of Bulgarian words (written in the Cyrillic alphabet) on signs and graffiti throughout the game (although some of these are words in other Slavic languages as well). One clear example is "цимент" ("cement") written across the top of some large buildings in Ravenholm and City 17 - the only language that spells this word in this way, using the Cyrillic alphabet, is Bulgarian. Many old cars scattered throughout the game are similar to ones commonly found in Eastern Europe, such as Moskvitchs, Trabants and Volgas. Also, during the game, Gordon comes to a Resistance settlement called "New Little Odessa." Odessa is a major city located on the coast of Ukraine, approximately 500 miles from Sofia.
Father Grigori has a name common to Eastern European countries and an accent that is stereotypically Eastern European. The naming of City 17 itself is similar to the Soviet practice of numbering secret closed cities rather than naming them. However, in addition to incorporating Eastern European elements, examples of Norwegian, Polish, Romanian, Swedish and French influences also exist, suggesting that the setting is something of a montage of European locations."