Simplify the following text for a Grade 11 native English-speaking person.
Original: Undoubtedly the geography of Greeceâ '' divided and sub-divided by hills , mountains and riversâ '' contributed to the fragmentary nature of ancient Greece .
Simplified: Undoubtedly the geography of Greeceâ '' divided and sub-divided by hills , mountains and riversâ '' contributed to the nature of ancient Greece .