very 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 Pas