The Alps.
The Alps in the northern part of the Italian peninsula provided a natural barrier to invaders. The Alps, however, were not insurmountable and incursion by barbaric tribes were part of early and late Roman history. Also, as formidable as these mountains were, the Carthage general Hannibal was able to cross the Alps with a large army and war elephants during the 2nd Punic War.
Carthage managed to cross the Alps with elephants, which Rome did not even attempt. B. Phoenicia
First of all it is not sure whether Spartacus and his followers wanted to cross the Alps to reach Gaul. This is an interpretation which was suggested by Plutarch, while Appian and Florus thought that he intended to march on Rome. However, it is more likely that the rebels were just trying to escape the Roman army and were plundering Italy to feed themselves. Moreover, they could not continue their rebellion for long. Once the Romans gathered a sufficient number of legions to suppress the rebellion, they had military superiority. Assuming that Spartacus did want to cross the Alps and managed to do so he might have continued to plunder the countryside until his defeat by the Roman army there, or he might have tried to get the local slaves to join his rebellion. However, there were much fewer slaves there than in Italy. In this case, it is also highly likely that he would have been eventually defeated.
The Alps provided protection against invaders from the north.
The Alps
The alps.
Napoleon crossed the Alps with on a Mule
The Alps
The Alps with an invading army .
He didn't.
The Alps.
never
The Rockies began first
by trying to get to the other side
The Alps.
On foot and elephants