Mining, livestock raising, and agriculture are the main economic activities, the latter being characterized by terrace cultivation on mountain slopes, which dates back to Roman times. The great arc of the Carpathians is accompanied by an outer fringe of rolling terrain known as the Subcarpathians and extending from the Moldova River in the north to the Motru River in the southwest. The area is densely populated, and there are serious economic development problems in remoter areas where there is little scope for further agricultural expansion. In the east, between the outer fringe of the Subcarpathians and the Prut River, lies the Moldavian Plateau, with an average height of 1,600 to 2,000 feet. In contrast to Transylvania, which experienced considerable urban development during the Dacian and Roman periods, Moldavia did not begin to develop towns until the Middle Ages, when the old Moldavian capitals of Iasi and Suceava had close commercial ties with towns in Transylvania and derived benefit from trade between the Baltic and Black Sea ports.
Plains cover a third of Romania, being the predominant form of relief in the south and west.
Their economic importance has increased greatly since the early 19th century. The whole region is covered by deposits of loess, on which rich, black chernozem soils have developed, this being essential for agriculture. The Danube floodplain is important economically, and along the entire stretch of the river, from Calafat in the west to Galati in the east, former marshlands have been diked and drained to increase food production. Willow and poplar woods border the river, which is important for fishing but much more so for commerce. On the northern edge of the Dobrogea region, adjoining the Moldavian Plateau, the great, swampy triangle of the Danube Delta is a unique physiographic region covering some 1,950 square miles, of which 1,750 square miles are in Romania.