The river forms a natural border between the two countries.

The Main river forms a natural border in the south.

As a consequence, there is no natural border between the two countries.

This has reduced the significance of natural borders over time.

This natural border, however was also the field of numerous conflicts.

To the south, the river Elbe forms a natural border.

The differences between natural and governmental borders goes together in many ways.

It is also a natural border, to the rest of the city Münchberg.

The valley of the Sims river is a natural border at the south.

There is no such thing as a natural border.