The surface of the vilayet is generally mountainous, except in the central valley of the Maritza, and along the banks of its tributaries, the Tunja, Arda, Ergene, &c. On the west, the great Rhodope range and its outlying ridges extend as far as the Maritza, and attain an altitude of more than 7000 f t.
The interesting little Rhodope veranyii, which has no odontophore, has been associated by systematists both with these simplified Opisthobranchs and with Rhabdocoel Planarians.
(1883); Bohmig, " Zur feineren Anatomic von Rhodope veranyi, Kolliker," Zeitschr.
The most distinguishing features of the country were the chain of Rhodope (Despoto-dagh) and the river Hebrus (Maritza).
The greater part of the country is hilly and irregular, though there are considerable plains; but besides Rhodope two other tolerably definite chains intersect it, one of which descends from Haemus to Adrianople, while the other follows the coast of the Euxine at no great distance inland.
Gumuljina is situated on the river Karaja-Su, south of the eastern extremity of the Rhodope range of mountains and 13 m.
The other mountain-systems display great complexity of formation; beginning with the Dinaric Alps and the parallel ranges of Bosnia, they run, as a rule, from north-west to south-east; the great chain of Rhodope traverses the centre of the Peninsula, throwing out spurs towards the Black Sea and the Aegean; farther west are the lofty Shar Dagh and the mountains of Montenegro and Albania, continued by the Pindus range and the heights of Acarnania and Aetolia.
The principal summits are Olympus overlooking the Gulf of Salonica; Musalla (9631) and Popova Shapka (8855), both in the Rhodope system; Liubotrn in the Shar Dagh (8989); Elin, in the Perin Planina (8794); Belmeken in southern Bulgaria (chain of Dospat, 8562); Smolika in the Pindus range (8445); Dormitor in northern Montenegro (8294); Kaimakchalan in central Macedonia (8255); and Kiona in Aetolia (8235).
The core is formed by the mountain masses of Rhodope, Belasitza, Perin and Rila; and here Palaeozoic and Mesozoic beds are absent, and the earliest sedimentary deposits belong to the Tertiary period and lie flat upon the crystalline rocks.
The Bulgarian Mahommedans, or Pomaks, who inhabit the valleys of Rhodope and certain districts in northern Bulgaria, are numerically insignificant; the Greek followers of Islam are almost confined to Crete.
In 1886 the informal union of Eastern Rumelia with Bulgaria was sanctioned by Europe, the districts of Tumrush (Rhodope) and Krjali being given back to the sultan.
Penetrating the difficult Rhodope country had carried out a vigorous offensive in several directions, as the result of which Adrianople was invested on the S.W.
Lately operating in the Rhodope came up, some by the Arda and some via Demotika on the S.