Complex sentence: The main entrance was believed to have been located at the northeast corner of the earthworks, and two other openings, one on the northwest and one in the southern section of the perimeter, permitted a small stream to flow between the rows of palisades.
Split into simpler sentences: The main entrance was believed to have been located at the northeast corner of the earthworks. Two other openings, one on the northwest and one in the southern section of the perimeter, permitted a small stream to flow between the rows of palisades.