Mehrauli in South Delhi is the most established living zone of Delhi. No, It isn't Purani Dilli around Red Fort or Chandni Chowk which is under 400 years of age. In reality, the most seasoned occupied part would be the Purana Qila, however that is not really living at this point. It is simply one more of the remnants of Delhi where just travelers come. 

Lal Kot

Origin of Delhi Name

Mehrauli Archaeological Park

Rajon Ki Baoli

Jamali Kamali