Simplify the following text for a Grade 11 native English-speaking person.
Original: At its greatest extent , the Empire comprised central Anatolia , the Levant , Mesopotamia , Persia , Turkmenistan , Pamir and the Indus Valley .
Simplified: At the height of its power , it included central Anatolia , the Levant , Mesopotamia , Persia , today 's Turkmenistan , Pamir and parts of Pakistan .