Simplify the following text for a Grade 7 native English-speaking person.
Original: Hildesheim , one of the oldest cities in the North of Germany , became the seat of the Bishopric of Hildesheim in 815 and may have been founded when the bishop moved from Elze to the Innerste ford , where it was an important market on the Hellweg trade route .
Simplified: Hildesheim is one of the oldest cities in North Germany . The city may have been founded when the bishop moved from Elze to the Innerste ford , where it was an important market on the Hellweg trade route .