Please answer the following question: Given the following passage  "While Harkness' original colleges were Georgian Revival or Collegiate Gothic in style, two colleges constructed in the 1960s, Morse and Ezra Stiles Colleges, have modernist designs. All twelve college quadrangles are organized around a courtyard, and each has a dining hall, courtyard, library, common room, and a range of student facilities. The twelve colleges are named for important alumni or significant places in university history. In 2017, the university expects to open two new colleges near Science Hill.",  answer the following question. Note that the answer is present within the text.  Question: What is the center of the colleges?
Answer:
a courtyard