Romania is a country in Southeastern Europe. It is bordered by Ukraine and Moldova in the northeast; Hungary and Serbia and Montenegro in the west and Bulgaria to the south along the Danube River. Romania has a stretch of sea coast on the Black Sea and the eastern and southern Carpathian mountains run through its centre. Romania has been an active member of NATO since 2004, and is also an acceding country to the European Union. The EU Accession Treaty was signed in early 2005, and Romania is due to join the European Union on January 1, 2007. Starting from January 1, 2007, Romania will be the seventh largest EU nation.