Simplify the following text for a Grade 7 native English-speaking person.
Original: The former borough of Mitte , located entirely within the former East Berlin , was combined with the boroughs of Wedding and Tiergarten ( both of which belonged to West Berlin ) to form the new Mitte borough .
Simplified: Mitte was the most central locality of Berlin ( Mitte is German for center ) . It was set up in 1920 , when GroÃ - Berlin was set up , and in 2001 it was joined with Wedding and Tiergarten to make a new borough called Bezirk Mitte .