Geography
The land area of Bulgaria is 110,550 square kilometers. The country is situated on the west coast of the Black Sea, with Romania to the north, Greece and Turkey to the south, Serbia and the Republic of Macedonia to the west. Considering its small size, Bulgaria has a great variety of topographical features. Even within small parts of the country, the land may be divided into plains, plateaus, hills, mountains, basins, gorges, and deep river valleys.
The total border is of about 2,264 kilometers. Rivers accounted for about 680 kilometers and the Black Sea coast for 400 kilometers; the southern and western borders are mainly defined by ridges in high terrain. The western and northern boundaries are shared with Serbia and Romania, respectively, and the Black Sea coastline constituted the entire eastern border. The Romanian border followed the Danube River for 464 kilometers from the northwestern corner of the country to the city of Silistra and then cut to the east-southeast for 136 kilometers across the northeastern province of Varna. The border with Greece is 491 kilometers long, and the Turkish border is 240 kilometers long.
Plains, valleys and mountains
The main characteristic of Bulgaria's topography is alternating bands of high and low terrain that extend east to west across the country. From north to south, those bands are the Danubian Plateau, the Balkan Mountains (called Stara Planina, meaning old mountains in Bulgarian), the central Thracian Plain, and the Rhodope Mountains. The easternmost sections near the Black Sea are hilly, but they gradually gain height to the west until the westernmost part of the country is entirely high ground.
More than two-thirds of the country is plains, plateaus, or hilly land at an altitude less than 600 meters. The average altitude in Bulgaria is 470 meters.
The Danubian Plateau extends from the Serbian border to the Black Sea. It encompasses the area between the Danube River, which forms most of the country's northern border, and the Balkan Mountains to the south. The plateau slopes gently from cliffs along the river, then it abuts mountains of 750 to 950 meters. The plateau, a fertile area with undulating hills, is the granary of the country.
The southern edge of the Danubian Plateau blends into the foothills of the Balkan Mountains, the Bulgarian part of the Carpathian Mountains.
The Balkan Mountains originate at the Timok Valley in Serbia and run southward towards the Sofia Basin in west central Bulgaria. From there they run east to the Black Sea. The Balkans are about 600 kilometers long and 30 to 50 kilometers wide. They retain their height well into central Bulgaria, where Botev Peak, the highest point in the Balkan Mountains, rises to about 2,376 meters. The range then continues at lower altitude to the cliffs of the Black Sea. Through most of Bulgaria, the Balkans form the watershed from which rivers drain north to the Danube River or south to the Aegean Sea. Some smaller rivers in the east drain directly to the Black Sea. The Sredna Gora (central hills) is a narrow ridge about 160 kilometers long and 1,600 meters high, running east to west parallel to the Balkans. Just to the south is the Valley of Roses, famous for rose oil used in perfume and liqueurs.
The southern slopes of the Balkan Mountains and the Sredna Gora give way to the Thracian Plain. Roughly triangular in shape, the plain originates at a point east of the mountains near Sofia and broadens eastward to the Black Sea. It includes the Maritsa River valley and the lowlands that extend from the river to the Black Sea.
The Rhodope Mountains occupy the area between the Thracian Plain and the Greek border to the south. The western Rhodopes consist of two ranges: the Rila Mountains south of Sofia and the Pirin Mountains in the southwestern corner of the country. They are the most outstanding topographic feature of Bulgaria and of the entire Balkan Peninsula. The Rila range includes Mount Musala, whose 2,975-meter peak is the highest in any Balkan country. About a dozen other peaks in the Rilas are over 2,600 meters. The highest peaks are characterized by sparse bare rocks and remote lakes above the tree line. The lower peaks, however, are covered with alpine meadows that give the range an overall impression of green beauty. The Pirin range is characterized by rocky peaks and stony slopes. Its highest peak is Mount Vikhren, at 2,915 meters the secondhighest peak in Bulgaria.
Rivers
The Balkan Mountains divide Bulgaria into two nearly equal drainage systems. The larger system drains northward to the Black Sea, mainly by way of the Danube River. This system includes the entire Danubian Plateau and a stretch of land running forty-eight to eighty kilometers inland from the coastline. The second system drains the Thracian Plain and most of the higher lands of the south and southwest to the Aegean Sea. Although only the Danube is navigable, many of the other rivers and streams in Bulgaria have a high potential for the production of hydroelectric power and are sources of irrigation water.
Of the Danube's Bulgarian tributaries, all but the Iskur rise in the Balkan Mountains. The Iskur flows northward to the Danube from its origin in the Rila Mountains, passing through Sofia's eastern suburbs and through a Balkan Mountain valley.
Several major rivers flow directly to the Aegean Sea. Most of these streams fall swiftly from the mountains and have cut deep, scenic gorges. The Maritsa with its tributaries is by far the largest draining all of the western Thracian Plain, all of the Sredna Gora, the southern slopes of the Balkan Mountains, and the northern slopes of the eastern Rhodopes. After it leaves Bulgaria, the Maritsa forms most of the Greek-Turkish border. The Struma and the Mesta (which separate the Pirin Mountains from the main Rhodopes ranges) are the next largest Bulgarian rivers flowing to the Aegean. The Struma and Mesta reach the sea through Greece.
Climate
Considering its small area, Bulgaria has an unusually variable and complex climate. The country lies between the strongly contrasting continental and Mediterranean climatic zones. Bulgarian mountains and valleys act as barriers or channels for air masses, causing sharp contrasts in weather over relatively short distances. The continental zone is slightly larger, because continental air masses flow easily into the unobstructed Danubian Plain. The continental influence, stronger during the winter, produces abundant snowfall; the Mediterranean influence increases during the summer and produces hot, dry weather. The barrier effect of the Balkan Mountains is felt throughout the country: on the average, northern Bulgaria is about one degree cooler and receives about 192 more millimeters of rain than southern Bulgaria. Because the Black Sea is too small to be a primary influence over much of the country's weather, it only affects the immediate area along its coastline.
The Balkan Mountains are the southern boundary of the area in which continental air masses circulate freely. The Rhodope Mountains mark the northern limits of domination by Mediterranean weather systems. The area between, which includes the Thracian Plain, is influenced by a combination of the two systems, with the continental predominating. This combination produces a plains climate resembling that of the Corn Belt in the United States, with long summers and high humidity. The climate in this region is generally more severe than that of other parts of Europe in the same latitude. Because it is a transitional area, average temperatures and precipitation are erratic and may vary widely from year to year.
The coastal climate is moderated by the Black Sea, but strong winds and violent local storms are frequent during the winter. Winters along the Danube River are bitterly cold, while sheltered valleys opening to the south along the Greek and Turkish borders may be as mild as areas along the Mediterranean or Aegean coasts.
