1. A Political Boundary:

* The Himalayas: The Himalayas form a natural boundary between India, China, Nepal, Bhutan, and Pakistan. This mountain range acts as a physical barrier, impacting trade, communication, and even cultural exchange.

2. A Geographic Boundary:

* The Andes Mountains: The Andes Mountains run along the western edge of South America, creating a distinct geographic boundary between the Pacific coast and the interior of the continent. This affects climate, vegetation, and the distribution of species.

3. A Biogeographic Boundary:

* The Rocky Mountains: The Rocky Mountains act as a biogeographic barrier, separating different plant and animal species found on the east and west sides. This is due to variations in climate, elevation, and soil conditions.

4. A Cultural Boundary:

* The Appalachian Mountains: The Appalachian Mountains, particularly in the US, have historically influenced cultural patterns and demographics. Different cultural groups have settled on either side of the mountains, contributing to variations in language, traditions, and values.

It's important to note that these are just examples. There are numerous other mountain ranges around the world that act as boundaries in various ways.