Simplify the following text for a Grade 8 native English-speaking person.
Original: Of Wilfrid 's Benedictine abbey , which was constructed almost entirely of material salvaged from nearby Roman ruins , the Saxon crypt still remains ; as does a frith stool , a 7th\/8th century cathedra or throne .
Simplified: The Benedictine abbey was built almost entirely of stones from nearby Roman ruins . The Saxon crypt still remains ; as does a frith stool , a 7th\/8th century ` cathedra ' or throne .