The exact boundary of this 300,000 km2, oval-shaped region is controversial and is debated by various experts continuously. The boundary given in this website more or less follows the book titled: Bulla B.-Mendöl T. 1999: A Kárpát-medence földrajza. Lucidus Kiadó. p. 420. (The Geography of the Carpathian Basin). It is possible that with further investigation and discussion with geography experts this presented boundary will change in the future and become more accurate. Now we briefly describe the main guideline of the boundary followed by the RBCB homepage. Starting in Orsova (south) the boundary of the Carpathian Basin is the Danube River. Towards the west until Beograd it then follows the Száva River westwards until Zagreb where it continues to the source of the Sotla River (Nizinska Hrvatska). Turning north it includes the Međimursko region of Croatia and the Prekmurje region of Slovenia as well as the entire county of Burgenland in Austria. From the lower Lajta River (north of Neusiedler See) area the boundary is a line towards the confluence of the Morva River with the Danube (formerly known as Porta Hungarica or in German: Hainburger Pforte). From here the boundary follows the national border of Slovakia, on the watershed line of the White Carpathians in the northwest. In the north the boundary more or less again follows the national border of Slovakia except for the catchment area of the Čierna Orava, which is partly in Poland. In the northeast the boundary reaches the Slovakian/Ukrainian border and then follows the watershed line of the Eastern Carpathians and including the ‘Carpathia’ parts (Закарпатська область) of Ukraine in the Basin. In the east the boundary follows the Romanian/Ukrainian border and then the watershed line of the Eastern and Southern Carpathians. Here the boundary also follows almost exactly the current county borders of Romania with minor corrections (Bicaz Gorge area). In the Mehedinţi Mountains of the Southern Carpathians the boundary follows the watershed line again all the way to the Danube on the opposite side of Orsova. The entire countries of Hungary and Slovakia are included in the Carpathian Basin.