Other minerals extracted include salt, kaolin, chalk, talc, asbestos, gypsum, mica, fluorite, quartzite, antimony, lime, sandstone, slate, and pyrites. The pyrites are plentiful and produce exportable quantities of sulfur and sulfur products. Fuel resources tend to be concentrated in basins and on lower lands; most other resources, both metal and nonmetal, are more frequently found in the Rodopi, the western Stara Planina, and in the other western highlands. Mineral waters are locally considered to be an important resource. The country boasts some 500 mineral springs, about one-half of which are warm or hot. Their mineral content varies, as does the concentration of the chemicals. The stronger of those considered medicinal are used for drinking only. The milder are used for drinking and bathing. Sofia has active hot springs that have been in use and have attracted people to the area for centuries. Its first settlement was built around such a spring. BOUNDARIES AND POLITICAL SUBDIVISIONS Boundaries Bulgaria has had nearly a century of modern independence, during which its borders have invariably been imposed upon it by others. This has been the case partly because the Balkan Peninsula was for many years a pawn in the balance-of-power politics of the more powerful European nations and also because Bulgaria has been on the losing side in three of its four major wars. It even fared badly at the peace table after the only war in which it emerged victorious (see ch. 2). In spite of these circumstances, the country has boundaries that have many natural physical characteristics and that have imposed no serious economic hardship on any significant group of people. They also contain a large percentage of the Bulgarian people, although numerous population resettlement movements have contributed to this end. None of its borders are officially disputed. The total boundary of Bulgaria is about 1,415 miles long. Rivers account for about 425 miles of it, the Black Sea coast for 248 miles, and a great portion of the remainder adheres to ridges in high terrain. The western and northern boundaries are shared with Yugoslavia and Romania, respectively, and the Black Sea coastline constitutes the entire eastern border. The southern boundary is shared with Greece and Turkey. Nationalists have territorial ambitions stemming from the size of the Middle Ages Bulgarian empire that encompassed about one-half of the Balkan Peninsula but, in the local political climate that has existed since World War II, such ambitions are not seriously considered. The post-World War I boundaries were established in rough detail by the Treaty of Peace between the Allied and associated powers and Bulgaria, signed in 1919 at Neuilly-sur-Seine. They were demarcated by international commissions between 1919 and 1922, formalized by the Treaty of Lausanne in 1923, and reconfirmed by the Treaty of Paris in 1947.