Simplify the following text for a Grade 5 native English-speaking person.
Original: Nippur ( Sumerian : Nibru , often logographically recorded as , EN . LÃ LKI , `` Enlil City ; '' Akkadian : Nibbur ) was one of the most ancient of all the Sumerian cities .
Simplified: Nippur was one of the most ancient of all the Sumerian cities .