Simplify the following text for a Grade 10 native English-speaking person.
Original: At York Minster there is , in the north transept , a cluster of five lancet windows known as the Five Sisters , each fifty feet high and still retaining ancient glass .
Simplified: At York Minster there are , in the north transept , a cluster of five lancet windows known as the Five Sisters , each fifty feet high and still have their ancient glass .