[Sidenote:  Piedmont towns and roads.]

Piedmont belts tend strongly towards urban development, even where rural settlement is sparse.  Sparsity of population and paucity of towns within the mountains cause main of traffic to keep outside the highlands, but close enough to their base to tap their trade at every valley outlet.  On the alluvial fans or plains of these valley outlets, where mountain and piedmont road intersect, towns grow up.  Some of them develop into cities, when they command transverse routes of communication quite across the highlands.  The ancient Via Aemilia traced the northern base of the Apennines from Ariminum on the Adriatic to Dertona at the foot of the Ligurian range back of Genoa, and connected a long line of Roman colonies.  The modern railroad follows almost exactly the course of the old Roman road,[1197] while a transverse line southward across the Apennines, following an ancient highway over the Poretta Pass to the Arno Valley, has maintained the old preeminence of Bologna.  A line of towns, connected by highways or railroads, according to the economic development of the section, defines the bases of the Pyrenees, Alps, Jura, Apennines, Harz, Vosges, Elburz and numerous other ranges.  Along the Elburz piedmont runs the imperial road of Persia from Tabriz through Teheran to Meshed.  In arid regions these piedmont roads are an unfailing feature, but their towns shrink to rural settlements, except at the junction of transmontane routes.

[Sidenote:  Piedmont termini of transmontane routes.]

Piedmont cities draw their support from plain, mountain and transmontane region, relying chiefly on the fertile soil of the level country to feed their large populations.  Sometimes they hug the foot of the mountains, as Bologna, Verona, Bergamo, Zurich, Denver and Pittsburg do; sometimes, like Milan, Turin, and Munich, they drop down into the plain, but keep the mountains in sight.  They flourish in proportion to their local resources, in which mineral wealth is particularly important, and to the number and practicability of their transmontane connections.  Hence they often receive their stamp from the mountains behind them as well as from the bordering plain.  The St. Gotthard route is flanked by Lucerne on the north and Milan on the south.  The Brenner has its urban outlets at Munich and Verona.  Narbonne and Barcelona form the termini of the route over the eastern Pyrenees; Toulouse commands the less used central passes, and Bayonne the western.  Tiflis is situated in the great mountain trough connecting the Black Sea and the Caspian; but over the Caucasus by the Pass of Dariel come the influences which make it a Russian town.  Peshawar, situated in the mountain angle of the Punjab, depends more upon the Khaibar Pass and its connections thereby with Central Asia than upon the plains of the Indus; its population, in appearance and composition nearly as much Central Asiatic as Indian, is engaged in traffic between the Punjab and the whole trans-Hindu Kush country.[1198]