Simplify the following text for a Grade 7 native English-speaking person.
Original: New enclosures , called henges were built , along with stone rows and the famous sites of Stonehenge and Silbury Hill reached their peak .
Simplified: Different pottery types such as Grooved ware appear during the later Neolithic ( c. 2900 BC -- c. 2200 BC ) whilst new enclosures , called henges were built , along with stone rows and the famous sites of Stonehenge , Avebury and Silbury Hill reached their peak .