Simplify the following text for a Grade 8 native English-speaking person.
Original: The secondary chain of the Alps follows the watershed from the Mediterranean Sea to the Wienerwald , passing over many of the highest and most famous peaks in the Alps .
Simplified: The main chain of the Alps follows the watershed from the Mediterranean Sea to the Wienerwald , defining the northern border of Italy . It then passes over many of the highest and most famous peaks in the Alps .