What are some of the ways that the physical and natural environment put limits on the directions and locations of trade routes in premodern times? 150 words at least pls

In Pre modern times terrain was certainly insurmountable most of the time so it dictated trade.

Explanation:

Before the invention of cars or trains there was the issue of transportation throughout the world.

The terrain defined which areas  could get which resources and not the independent people of the region who would wish for something but could not have it because the place where that thing would be is across a mountain range.

This is the reason why ancient trade routes exist that were tried and tested and were known to be easy to walk on.