Simplify the following text for a Grade 9 native English-speaking person.
Original: The orchestra , which had an average diameter of 78 feet , was situated on a flattened terrace at the foot of a hill , the slope of which produced a natural theatron , literally `` watching place '' .
Simplified: The orchestra was on a flattened terrace at the foot of a hill , the slope of which produced a natural theatron , ( watching place ) .