Large fields of oil and natural gas are the most important sub-surface assets. Both are of the best quality in Europe, with the possible exception of those near Baku in the Soviet Union. Liquid petroleum is pumped from large fields in the Ploiesti area and also from an area in central Moldavia. Natural gas is available under a large part of the Transylvanian plateau. A few minerals, such as lead, zinc, sulfur, and salt, are available in quantities needed domestically, but iron and coal are not plentiful. Deposits of lignite, gold, and several other minerals occur in concentrations having sufficient value to be mined. BOUNDARIES AND POLITICAL SUBDIVISIONS Boundaries When it gained full independence in 1878, Romania contained the historic provinces of Moldavia and Walachia, some of Bessarabia, and a portion of Dobruja. Substantial numbers of Romanians remained outside the original state's boundaries in Transylvania and in the Russian portion of Bessarabia. The first boundaries remained little changed until after World War I, although the strip of Dobruja was enlarged somewhat in 1913, after the Second Balkan War (see ch. 2). In the 1918 settlement after World War I about 38,500 square miles were ceded to Romania from the dismantled Austro-Hungarian Empire. In addition to historic Transylvania, with its area of about 21,300 square miles, a strip along its western side, with a substantially Magyar population, and Bukovina, part of which is now the most north-central section of the country, were included. Also in the aftermath of World War I and the Russian revolution, Romania acquired Bessarabia from the new Bolshevik regime and enlarged its holdings in Dobruja at Bulgaria's expense. During the brief period of accord between the Soviet Union and Nazi Germany immediately before World War II, portions of Romania were sliced away and divided among Hungary, Bulgaria, and the Soviet Union. The post-World War II settlement, arrived at in 1947, again transferred Transylvania from Hungary to Romania, and Dobruja--with a somewhat modified southern border--was transferred from Bulgaria. The Soviet Union retained all of Bessarabia and the northern portion of Bukovina. In 1971 none of Romania's borders were disputed, and all of them were satisfactorily demarcated. The total circumference of the country is about 1,975 miles. The northern and eastern border with the Soviet Union extends for about 830 miles; the southern border with Bulgaria, for 375 miles; the southwestern border with Yugoslavia, for 345 miles; and the northwestern border with Hungary, for 275 miles. The Black Sea coast is about 150 miles long. The eastern boundary generally follows the Prut River, and most of the southern boundary is formed by the Danube; in the west and north the border follows no distinctive terrain features, often having been drawn according to ethnic, rather than geographic, considerations. Political Subdivisions