Albania and Bulgaria are in Balkan Peninsula; Romania is outside, on the north of Danube.
Italian peninsula
Serbia is located in Central-Southeastern Europe, and borders Hungary, Romania, Bulgaria, Macedonia, Bosnia-Herzegovina, Montenegro and Croatia.
Ukraine Romania Bulgaria turkey
Bulgaria, Romania, Ukraine, Russia, Georgia and Turkey.
It is in south eastern Europe, north of Romania
For example: Italy, Austria, Romania.
Ukraine Russia Georgia Turkey Bulgaria Romania
Romania, Bulgaria, Serbia, Austria-Hungary, Montenegro, Greece, and the Ottoman Empire.
Albania, Bosnia & Herzegovina, Bulgaria, Greece, Macedonia and Montenegro are all fully located on the Balkan Peninsula. Croatia, Serbia, Romania, Slovenia and Turkey are partially located on the peninsula.
South of Danube, Southern Europe (Europe ends at the URAL mountains!)
Bulgaria is directly south of Romania.