Simplify the following text for a Grade 9 native English-speaking person.
Original: Charlottenburg is located along the river Spree within the Berlin-Warsaw glacial valley , west of the Tiergarten park .
Simplified: Charlottenburg is located in Berlin 's inner city , west of the Tiergarten park . Its historic core Alt Lietzow is situated near the river Spree within the Berlin-Warsaw glacial valley .