To be a 24 hour city means either relaxing expectations of quietude at night or to reduce the noise that people make during the late and early hours.
For parks there is only one place to go...down under.....if quietude is to be maintained.
Placing facilities and plant life underground will add another dimension to the park experience as people will be able to follow their natural biological rhythms and inclinations....night-owls, insomniacs, etc., need not be neglected anymore in park design.
Double doors and noise cancelation technology will work together to make the underground developments trully quiet places where people can gather to have fun or relax without bothering those sleeping nearby, at all hours of the day and night.