Simplify the following text for a Grade 7 native English-speaking person.
Original: Another reason why many drivers consider Interlagos interesting is that it was not built on flat terrain , but follows the ups and downs of hilly ground , which makes it harder to drive and demands more power from the car 's engines .
Simplified: Another feature that makes Interlagos interesting is that it follows the ups and downs of hilly ground . This makes the circuit harder to drive and more demanding on the car 's engine .