How does the countryside change after the first few weeks of travel in The Hobbit?
In Chapter 2, when the dwarves and Bilbo and Gandalf begin their adventure, they quickly leave civilised lands behind them and enter a far rougher, more dangerous part of Middle Earth:
Now they had gone on far into the Lone-lands, where there were no people left, no inns, and the roads grew steadily worse. Not far ahead were dreary hills, rising higher and higher, dark with trees. One some of them were old castles with an evil look, as if they had been built by wicked people. Everything seemed gloomy, for the weather that day had taken a nastly turn.
Note how the description adds to the sense and feeling of imminent danger, that of course the company soon discovers in the form of the trolls. The absence of signs of civilisaion is mentioned, and it is important to take into consideration how nature is described. The hills are "dreary" and imposing in their seemingly endless height. They are also "dark" and the castles have an "evil" look. The weather too, in a kind of pathetic fallacy adds to the dangerous atmosphere with its "nasty turn". Thus the setting is laid for the dangerous events the company are about to face.