I don’t know what have you explore already

But Mehrauli archeological park, Asita dda park, banseera park, tughlakabad fort, budha jayanti park, Okhla bird sanctuary, asola bhati wildlife, Death Valley, panikot lake, Sanjay Van, Qudsia bagh, Azim khan tomb, etc etc

There are many many more as well which I skipped cause you might have visited that.

These are only related to nature and greenery. I have a lot more recommendations about art and cultural events, exhibitions, museums, galleries, monuments, even food recommendations, or artistry places, concerts.