Walachia, in the south, contains the southern part of the Transylvanian Alps--called the Southern Carpathians by Romanian geographers--and the lowlands that extend between them and the Danube River. West to east it extends from the Iron Gate to Dobruja, which is east of the Danube in the area where the river flows northward for about 100 miles before it again turns to the east for its final passage to the sea. Walachia is divided by the Olt River into Oltenia (Lesser Walachia) in the west and Muntenia (Greater Walachia), of which Bucharest is the approximate center, in the east. Nearly all of the Walachian lowlands, except for the marshes along the Danube River, and the seriously eroded foothills of the mountains are cultivated. Grain, sugar beets, and potatoes are grown in all parts of the flatland; the area around Bucharest produces much of the country's garden vegetables; and southern exposures along the mountains are ideally suited for orchards and vineyards. The Transylvanian Alps have the highest peaks and the steepest slopes in the country; the highest point, with an elevation of about 8,340 feet above sea level, is 100 miles northwest of Bucharest. Among the alpine features of the range are glacial lakes, upland meadows and pastures, and bare rock along the higher ridges. Portions of the mountains are predominantly limestone with characteristic phenomena, such as caves, waterfalls, and underground streams. Transylvania, the northwestern one-third of the country, includes the historic Transylvanian province and the portions of Maramures, Crisana, and Banat that became part of Romania after World War I. The last three borderland areas are occasionally identified individually. Nearly all of the lowlands in the west and northwest and the plateau in the central part of the province are cultivated. The western mountain regions are not as rugged as those to the south and east, and average elevations run considerably lower. Many of the intermediate slopes are put to use as pasture or meadowland but, because the climate is colder, there are fewer orchards and vineyards in Transylvania than on the southern sides of the ranges in Walachia. Forests usually have more of the broadleaf deciduous tree varieties than is typical of the higher mountains, but much of the original forest cover has been removed from the gentler Transylvanian slopes. Dobruja provides Romania's access to the Black Sea. The Danube River forms the region's western border, and its northern side is determined by the northernmost of the three main channels in the Danube delta. The line in the south at which the region has been divided between Romania and Bulgaria is artificial and has been changed several times.