city center vs plaza

city center

noun
  • The central business and shopping area of a city. 

plaza

noun
  • A shopping mall. 

  • A town's public square. 

  • A strip mall. 

  • An open area used for gathering in a city, often having small trees and sitting benches. 

How often have the words city center and plaza occurred in a corpus of books? (source: Google Ngram Viewer )