Simplify the following text for a Grade 7 native English-speaking person.
Original: Bex sits on the east side of the Rhone River in a wide valley surrounded on the east by the Bernese Alps and west by the Chablais Alps .
Simplified: Bex sits on the east side of the Rhone River in a big valley bordered on the east by the Bernese Alps and west by the Chablais Alps .